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Forensic Palynology: A New Way to Catch Crooks

Vaughn M. Bryant, Jr.
Palynology Laboratory
Texas A&M University
College Station, Texas 77843

Dallas C. Mildenhall
Institute of Geological and Nuclear Sciences
P.O. Box 30368
Lower Hutt, New Zealand

Abstract

Studies of palynomorphs trapped in materials associated with criminal or civil investigations are slowly gaining recognition as valuable forensic techniques.  Today, the country of New Zealand leads the world in the use of forensic palynology, and the acceptance of this type of evidence in courts of law. To illustrate how important, and diverse forensic palynology has become, we have briefly examined a number of actual circumstances where these types of techniques have proven useful. In most of these cases the palynomorph data were an important factor in either solving the case, or they were used to identify and link a suspect to the scene of a crime. We also discuss some of the strengths, and weaknesses, of using forensic pollen data, and why we feel this technique is still neither widely accepted nor used in most of the countries of the world.

Introduction

During most of 1994 and 1995, one of the most publicized court cases in history made front-page headlines in newspapers and magazines all over the world. This was the murder trial of the famous football and movie star O.J. Simpson that ended in October, 1995 when the jury found the defendant innocent.

Mr. Simpson was accused of killing his wife and one of her friends during a rage of jealousy. News stories reported that the trial became so popular as a media event that over one and one-half million people watched it daily on TV. During those court proceedings, some of the most important items of evidence were forensic samples of fibers and hairs, and DNA analyses of blood-stained clothing and blood found at the crime scene, in the defendant's car, and in his home.

In spite of all the television coverage and media attention, both the prosecution and defense missed one potentially valuable piece of evidence--forensic pollen evidence that might have been attached to the defendant's clothing. Had the clothing that Simpson supposedly wore on the night of the crime been examined, it might have contained certain types of pollen that the prosecution could have used to link the suspect to the scene of the crime. If the examination revealed no pollen, that evidence could have been used by the defense to argue that the defendant was not at the scene of the crime.

Testimony during the Simpson trial suggested that the person, or persons, who committed the double murder may have hidden in bushes in front of the Simpson home waiting for the victims. If this assumption is correct, it is possible that pollen from the flowers on the bushes, or pollen that may have fallen from the flowers onto the bushes' leaves might have brushed off on the assailant's clothing. If that occurred, then it would have left a "pollen fingerprint" on the person's clothing that could have linked the killer to the crime scene.

The term "forensic palynology" refers to the use of pollen and spore evidence in legal cases (Mildenhall, 1982). In its broader application, the field of forensic palynology also includes legal information derived from the analysis of a broad range of microscopic organisms--such as dinoflagellates, acritarchs, and chitinozoans--that can be found in both fresh and marine environments (Faegri et al., 1989).  However, in most sampling situations forensic palynologists rarely encounter these other types of organisms because most are restricted to fossil deposits.

It is difficult to establish precisely when the field of forensic palynology began. Attempts made prior to he 1950's, whether successful or not, probably did not gain much public attention and therefore were not reported. Or, it is possible that if earlier attempts were made, the results may have been purposely hidden from the media in order not to alert criminals about the use of this new technique.

Two of the earliest reported cases using forensic palynology occurred in 1959--one in Sweden and the other in Austria (Erdtman, 1969). The case in Sweden revolved around a woman who was killed in May, during a trip in central Sweden. During the court hearing , a number of experts, including a palynologist, were asked to examine dirt attached to the woman's clothing. The objective of those studies was to determine whether or not the woman was killed where she was found, or if she had been killed elsewhere and then dumped at the site where her body was discovered. Preliminary studies of the pollen in the dirt samples suggested that she had been killed elsewhere because the dirt lacked pollen from plants common in the area where the body was found (i.e. Plantago, Rumex and grasses). However, a later reinterpretation of the forensic pollen samples noted that the murder could have occurred in May because that was before the grasses and herbs in the region had pollinated. The two opinions were both entered as evidence in the court proceedings, but we do not know if the murder was ever solved. The importance of this case is that it is one of the earliest records in which pollen data were considered as important forensic evidence in a court case.

In the second case, which occurred in Austria, the discovery of the murdered victim's body, and the conviction of the criminal were based primarily on the evidence recovered from a pollen sample associated with the crime. During a vacation along the Danube River, a man disappeared near Vienna, but his body could not be found. The police soon found a suspect with a motive for killing the missing person, but had no evidence to link the person with the possible crime. Without a confession or a body, the prosecutor's case seemed hopeless.

As the investigation proceeded, a search of the suspect's room revealed a pair of boots with mud still attached to the soles. These were taken as evidence and given to Wilhelm Klaus, a geologist with the Austrian Geological Survey, for analysis. Dr. Klaus examined the mud and found that it contained modern spruce, willow, and alder pollen. In addition there was a special type of 20 million-year-old, Miocene-age fossil hickory pollen grain present in the mud.

Based on the pollen evidence, Dr. Klaus was able to pinpoint where the defendant must have walked while getting mud on his boots. Only one location, a small area 20 kilometers north of Vienna along the Danube Valley, had soils that contained the precise mixture of pollen found in the boots' mud. When confronted with the identity of this location, the shocked defendant confessed his crime and showed the authorities where he had killed the victim and then buried the body, both of which occurred in the precise region pinpointed by Klaus.

In other early cases, during the 1960s and 1970s, Max Frei, a noted Swiss criminalist, often used pollen as a forensic tool to link suspects to events or to crime scenes (Palenik, 1982). Some of his most noted cases include one in which a suspect claimed that his pistol could not have been used to commit a recent murder because it had not been removed from its storage box in months. However, Dr. Frei proved the suspect was lying because grease on the pistol contained alder and birch pollen, both of which were pollinating when the murder occurred, not when the suspect claimed he had last cleaned the pistol and put it away. In another case Dr. Frei showed that a document was a forgery because he found fall-pollinating cedar pollen stuck to the ink used to sign a document, which had a June date (Newman, 1984). Max Frei also gained fame for his pollen analysis of the Shroud of Turin, which revealed that the Shroud had probably been kept for some time in Israel and Anatolia (Wilson, 1978).

More recently, the forensic analysis of pollen grains has been used as a theme in a fictional murder mystery novel called Probable Cause (Pearson, 1991). According to the author, the identification of specific pollen grains found attached in the earwax of a murdered person was significant enough evidence to link the suspect to the murder, and to "swing the jury and win a conviction."

Discussion

Why does it work?

Pollen and spore production and dispersion are important considerations in the study of forensic palynology. First, if one knows what the expected production and dispersal patterns of spores and pollen (called the pollen rain) are for the plants in a given region, then one will know what type of "pollen fingerprint" to expect in samples that come from that area (Bryant, 1989). Therefore, the first task of the forensic palynologist is to try to find a match between the pollen in a known geographical region with the pollen in a forensic sample. Knowledge of pollen dispersal and productivity often plays a major role in solving such problems.

There are a number of different methods by which plants disperse their pollen or spores. Many aquatic angiosperms live completely submerged and release their pollen underwater, relying on water currents to transport the pollen from the male anther to the female stigma of a neighboring flower. This method of transport, like the wind, is a hit- and -miss method of pollination. For this reason these plants produce pollen types that consist only of a single-layered cellulose wall, the pollen is almost never preserved in sediments and generally oxidizes rapidly if removed from water. Because of these limitations, these types of pollen are of little potential value for forensic work.

Another small group of plants are called "autogamous" because they are self-pollinating and are so efficient that little pollen is needed. Most plants in this category produce less than 100 pollen grains per anther. Pollen from these plants is rarely dispersed into the atmosphere even though their pollen preserves well and has a durable outer wall, called an "exine," made of a stable chemical compound called "sporopollenin." Like pollen produced by submerged plants, the pollen of autogamous plants is of little value in forensic work because it is dispersed in minimal numbers.

In a larger group of plants, called zoogamous plants, pollination is dependent upon the transport of pollen by some type of insect (i.e., bee, wasp, beetle, moth, ant) or animal (i.e., hummingbirds, lizards, nectar-feeding marsupials and bats, or other small mammals). Because of the efficiency, pollen productivity is low, yet not as low as is found in autogamous plants. The potential value of zoogamous pollen in forensic work is excellent for two reasons. First, zoogamous pollen grains have some of the most durable exines. This means their pollen often will remain preserved in deposits for long periods of time and are generally less susceptible to destruction than pollen grains dispersed by other methods. Second, zoogamous pollen is produced in low amounts, thus is not normally a potential contaminate found in the pollen rain of an area. This last point is both good and bad. It is good because if the pollen of a zoogamous plant is found in a forensic sample, there is a high degree of confidence that the pollen belongs with the forensic sample and is not an atmospheric contaminate. It is bad because so little pollen is produced by each plant that the chances of its pollen getting into a forensic sample are reduced.

The last category is the wind-pollinated (anemophilous) types. This group includes a wide range of producers such as the gymnosperms and a significant number, but not a majority, of the angiosperms. Also included in this group are spore-producing plants such as fungi, ferns, and mosses. Because wind pollination is the most inefficient method of dispersion, anemophilous plants must produce vast quantities of light-weight grains that will travel easily in air currents. Some species of wind-pollinated plants, such as marijuana (Cannabis), produce as many as 70,000 pollen grains per anther (Faegri et al., 1989). When large fields of these anemophilous plants grow together, their flowers can produce millions of pollen grains that are dispersed daily during the flowering season. In many cases, this abundance becomes a disadvantage because often marijuana pollen occurs in trace amounts on the shoes of people connected with the drug trade. Nevertheless, when such evidence is found, a palynologist cannot state in court that "traces of Cannabis pollen could only have come from direct association with, or use of, the actual plant." Instead, if asked, a palynologist would have to admit that traces of marijuana pollen on a suspect's shoes could have come from almost anywhere as a result of "random air dispersal" of that plant's pollen. An example of this occurred during the summer of 1995 when European newspapers reported that "clouds" of Cannabis pollen were drifting across the Mediterranean from source areas in Morocco, where local farmers reported growing a bumper crop of marijuana. European residents along the Mediterranean coast were also warned by local newspaper not to breath "too much" of the Cannabis pollen because it could cause hallucinations. This last statement, however, is completely false because Cannabis pollen does not contain any of the hallucinogenic cannaboids. Nevertheless, the high atmospheric counts of Cannabis pollen illustrate how some of these grains might accidentally occur in some forensic samples.

Another important factor is the "sinking speed" or rate at which a pollen grain falls to earth. Marijuana, alder, juniper and birch pollen are very small and very light. Their average fall rate is about 2cm per second. On the other hand, maize plants and fir trees produce pollen that are large and heavy, and fall to earth at a rate 15 times faster than the lighter ones. Using just these two examples, one can see that the potential distribution area of maize and fir pollen grains will be smaller and more restricted that the dispersion area covered by the pollen from plants in the first category (Tauber, 1967). In forensic studies this means that when maize and similar types of large pollen grains are found in samples, small dispersion areas are indicated and greater precision in identifying the source region may be possible.

The way in which samples are collected and processed is also critical, and both must be done correctly to obtain accurate results. Ideally, pollen samples should be collected by a competent palynologist knowledgeable in the field of forensics. Such individuals will know how to collect contamination-free samples, and will know what precautions should be taken to ensure that samples remain contamination-free throughout the storage, laboratory extraction phase, and the analysis process. It is also important to keep accurate records of how each sample is collected and what has happened to each sample from the time of collection until the completed analysis and report are presented.

Security is another essential concern. To ensure the court admissibility of forensic evidence, it is critical that a palynologist be able to state under oath that the materials, and the subsequent pollen samples collected from those materials, were stored in a locked and secure location. This aspect is also essential to avoid the accusation that someone else, who was not authorized, gained access to a sample and "switched" it. If any hind of contamination or switching, either natural or intentional, can be proven or implied, then doubt will be cast upon the resulting interpretations (Skinner et al., 1988).

One final concern is the amount of material that will be collected for forensic analysis. In most cases very little dirt, mud or other debris is available for collection and analysis. Therefore, most forensic palynologist face several immediate problems. First, they will generally not have enough sample to experiment with different extraction techniques to determine which works best. Second, the will often not have enough sample to conduct a second test if something goes wrong (i.e., a centrifuge tube breaks, a beaker spills, or a microscope slide breaks). Third, sample size may be further reduced when other potentially useful tests may need to be carried out first (i.e., soil testing, searches for fibers, sand grain analysis) before a destructive pollen analysis can be attempted.

What to Sample?

Sediment--Soil, dirt, and dust are common elements at almost every crime scene. As such they should be collected carefully because often these elements contain abundant pollen and spores (Pain, 1993). Samples of dirt collected from the clothing, skin, hair, shoes, or car of a victim might prove useful in linking the victim with the location where the crime occurred (Mildenhall, 1988). The same would be true of any suspects thought to be associated with a crime. Mud found on a stolen vehicle, or a vehicle used in a crime, could link the vehicle with the scene of a crime or link it to the place from which it was stolen. Dirt found associated with other objects or other types of conveyances (i. e., airplane, bicycle, motorcycle, boat, etc.) thought to be associated with a crime also might yield pollen evidence useful in linking those items with a specific crime or a specific geographical locale (Brown and Llewllyn, 1991).

Examples of where these types of soil, dirt, or dust samples should be collected are numerous. Common sense and an awareness of what type of data one might hope to recover from dirt samples should become a primary guide for collection. In addition, steps must be taken to ensure that samples don not become contaminated. Examples include:

Example 1: The following was used as a central plot in a television program. It is not an actual court case. Nevertheless, the data, as presented, represents a valid situation where pollen could be used effectively in a real court case.

The location is the Hawaiian Island of Oaju. A van is stolen form a car dealer in downtown Honolulu and is driven to a hideout located in the Koolau Mountains. Several weeks later the van is used in a Honolulu bank robbery and then it is abandoned near the scene of the crime. The police find the van, but have no clues as to the identity of the thieves or where they might be hiding. Because the airport and harbor are being watched, the police believe none of the suspects have left the island.

A search of the vehicle for various kinds of forensic evidence offers no clues. As part of the investigation, dirt samples from one of the van's fenders are collected and sent to the forensic laboratory. The air filter from the van's carburetor is also removed and sent to the forensic laboratory for study.

Pollen and spores recovered from the van's fender and from the van's air filter contain pollen from trees that grow abundantly in the Koolau Mountains, and spores form small tropical ferns that grow on the shaded forest floor of the Koolau Mountains. Based on these bits of evidence, the police began a search of the Koolau Mountain region and asked local store owners or residents if they had seen the van, or any suspicious- looking people in their region. A lead from a local convenience store worker sends the police to a small cabin in a remote region of the Koolau Mountains where they surround and catch the bank robbers.

Example 2: A thief robbed a store and escaped on a motorcycle. Police gave chase and almost caught the thief, but at the last minute the thief abandoned his motorcycle and ran up a muddy hill and escaped into a wooded area. The next day a man went to the local police headquarters and reported that his motorcycle had been stolen the day before. Because the motorcycle claimant was about the same size and build of the thief, the police considered him to be their prime suspect. However, they were unable to link him with the crime. Armed with a search warrant, the police searched his house. They could find none of the items that had been stolen, but they did collect a pair of muddy boots owned by the suspect. When asked about the mud, the suspect said that the mud came from a farm where he worked and denied that the mud could have come from the hill where his motorcycle had been abandoned.

Dirt samples from the suspect's boots were sent to the forensic laboratory for analysis. Also collected, and sent to the forensic laboratory, were "control" soil samples of mud collected on the hillside where the motorcycle was abandoned, and mud from the farm where the suspect worked. The pollen types recovered from the mud on the boots closely matched the pollen types recovered from the mud on the hillside. In addition, the pollen types from the mud on the boots were quite different from the pollen types found in the control soil samples collected on the farm. In spite of the convincing pollen evidence, the suspect was released because the court remained unconvinced that forensic pollen studies were truly accurate enough to link the suspect to the hillside where the motorcycle had been abandoned (Mildenhall, 1990).

Example 3: A group of young ladies were walking along a remote beach when they were approached by some young men who insisted on joining them, in spite of the ladies' request that the men leave. Later a passing motorist noticed a lady wandering down a dirt road leading from the beach to a nearby highway. Her clothes were torn and wrinkled, and she seemed to be in a confused and distressed mental state. The motorist drove her to the nearest police station where she regained her composure and then reported that after leaving her girl friends, she had continued walking along the beach, and that she was attacked and sexually assaulted by one of the men who had been bothering them earlier in the afternoon. The next day the police arrested a suspect and the lady identified her attacker in a police line-up. The police were fairly sure they had arrested the right person, but were unable to hold him in jail because they had no other evidence. In addition, three of his male companions all testified that he could not have been on the beach when the assault occurred because he had been with them all day, and that none of them had been near the beach. A search of the suspects's apartment revealed a pair of sneakers, which had been wiped fairly clean. However, caught in the tread was a small amount of fresh mud. The mud was collected and sent to the forensic laboratory for analysis. A study of the mud's contents revealed pollen and spores from plants that commonly grow on beach dunes where the assault occurred. However, that evidence alone was not enough to link the suspect with the "precise" beach where the assault occurred. Further studies of the mud revealed samples of a shallow-water dinoflagellate, which was common "only" in the tidal flats along the beach where the assault occurred. Thus, the pollen and spore evidence linked the suspect to a beach, but the dinoflagellate cysts linked the person to the precise beach where the assault occurred. Based on the evidence, the suspect later admitted he committed the assault.

Hair and Cloth--Woven cloth, woolen blankets, ropes, clothing and fur all make excellent traps for pollen and spores. Woven materials and fur are made of tiny interwoven fibers. When air comes in contact with woven materials, the fibers become filters that retain solid particles, such as pollen and spores. Woolen garments, including blankets, skirts, suits, ties, and sweaters, make the best pollen and spore traps. However, hair, whether human or animal, remains one of the very best pollen and spore traps.

When wind blows through hair, pollen in the wind becomes trapped in the open spaces between individual strands. In humans, the addition of various types of hair sprays, natural oils, and tonics makes hair surfaces sticky and provides an even better trap for pollen and spores. Hair from a victim, or suspect, can be sampled for its pollen by carefully washing it with detergents and warm, distilled water. This process will loosen trapped pollen and free it from sticky hair surfaces. Once collected, the wash water can be stored before analysis in a sterile container that is tightly closed and frozen, or a small amount of alcohol can be added to retard microbe growth. Hair sampling need not be restricted to humans. Fur rugs found at a crime scene might have been used for wiping shoes and thus may be rich in pollen and spores. Domestic pets, sheep, cattle, horses, or other fur-bearing animals that might be associated with a crime scene or might be stolen or lost ma be traced to their original owner through the analysis of pollen and spores attached to their hair. Hair on fur coats, felt hats, or sheep skins sometimes used as car seat covers are also excellent pollen traps and should be considered for their potential use as forensic samples.

Several actual court cases illustrate how forensic pollen data collected from the clothing of victims and suspects became important clues that helped obtain convictions.

Example 1: A woman was kidnapped at knife-point while jogging in a city park. She was dragged to a nearby wooded area where she was assaulted and then killed. A man who lived near the park had been seen walking near the jogging trail in the park just before the time the woman disappeared. When questioned by police, the man admitted being in the park, but said he had not seen the victim and had never been in the nearby woods. A police search of the suspect's apartment revealed a dark woolen sweater and a pair of soiled pants that they believed he may have worn while committing the assault. A forensic pollen analysis of the sweater and pants revealed that each garment contained a slightly different combination of pollen and spores, yet both were rich in pine pollen and fern spores. Forensic pollen studies of surface soils collected from the crime scene contained large amounts of both pine pollen and fern spores, as did the soiled shorts worn by the murdered woman. The forensic pollen "fingerprint" of the woman's shorts was almost identical to the forensic pollen "fingerprint" extracted from the suspect's sweater and from his soiled pants. All three forensic samples were consistent and revealed that the only way so much pollen and spores could have gotten on the clothing was by "rolling-around" on the ground in the wooded area. Because there were no other nearby locations where both pine trees and ferns grew together, as they did in the wooded area, the pollen "fingerprint" became important evidence in obtaining a conviction (Mildenhall, 1992).

Example 2: Recently the body of a murdered victim was found in a ditch by the side of a rural highway. All identification from clothing and from the victim had been removed, the victim's face had been beaten, and the hands and feet cut off to prevent a fingerprint or footprint identification. Because there was no blood spilled into the soil where the body was found, it was determined that the victim had been killed elsewhere and then the body was discarded by the side of the highway. With no clues to work with, the police were not even sure where the crime had been committed, or where the victim may have lived. Forensic pollen samples were collected from the victim's shirt, pants, socks, and shoes. In addition, four separate samples of the surface dirt were collected from the location where the body was found. The pollen types and percentages in each of the surface soil samples were similar. As a group, however, they did not exactly match the pollen "fingerprint" recovered from the various clothing items worn by the victim. The slight difference between the samples (clothing and soil) indicated that the victim may have lived some distance from where the body was found. Additional regional pollen studies produced one near-perfect pollen match with the victim's clothing. It suggested that the victim probably lived (and may have been murdered) approximately 150 miles north of where the body was found. This information helped police narrow the search for the victim's identity, and for his murderer. This case is still ongoing at this time (Bryant et al., 1990).

Example 3: A rural farmer living in the American Midwest was kidnapped, robbed and then murdered. The victim's car was stolen, but later abandoned when it got stuck in mud near a busy highway. The next day a drifter was arrested in a nearby town for breaking into a closed liquor store. While in jail awaiting trial, the drifter told a fellow prisoner he wouldn't be in jail if his car hadn't gotten stuck in the mud some 30 miles south of town. The other prisoner, hoping to work a deal for a lighter sentence, told this story to the sheriff. Based on this new information, the drifter was returned to the crime scene where the murder occurred, and to the town where the murder victim lived. However, even under intensive questioning, the drifter revealed no clues that would link him to the crime. One of the investigators noticed that there was a large corn field between the dirt road where the car had been abandoned and the nearby highway leading to the next town. A forensic pollen analysis of the drifter's shirt and pants, removed and stored when he had first been arrested, revealed that both were covered with fresh corn pollen, and that the neck and shoulder region of the shirt had the highest concentration of corn pollen. The forensic pollen data indicated that the drifter had recently walked through a corn field similar to the one between the abandoned car and the highway. This evidence, combined with several eyewitness accounts from neighbors who had seen the drifter walking along the highway near where the car had been abandoned, confirmed that the drifter had been in the area where the crime was committed and where the car was abandoned. While awaiting trial , additional evidence and several fingerprints firmly linked the drifter to the murder.

Example 4: A rustler stole 300 sheep from a ranch and left no clues. Several weeks later a rancher took 350 sheep to an auction for sale. However, the auctioneer became suspicious because he knew the rancher barely had enough pasture land to support 200 sheep, not the 350 he was trying to sell. The 350 sheep were impounded, and the person who had his sheep stolen was asked to identify the impounded sheep. He believed they "might" be his sheep, but he had not branded them, so there were no identifying marks that would prove they were his. The rancher who put the sheep up for sale insisted that he had bought the sheep a week earlier, but could not produce a bill of sale nor would he say where he had purchased them. Police sheared wool from small areas on the backs of several of the impounded sheep, then sent the wool to the laboratory for pollen analysis. The pollen spectra recovered from the sheared wool matched the types of plants that grew in the field where the sheep were stolen, not in the pasture owned by the person who had tried to sell the sheep at auction. Thus, the pollen evidence confirmed that almost all of the impounded sheep (300 of them) were indeed the ones that had been stolen from the first rancher.

Example 5: A shipment of Persian rugs arrived in the United States and was examined by custom agents. The custom agents suspected the rugs were made in Iran (a country from which imported goods were not allowed), even though the owners claimed the rugs had been made in Egypt. Agents uses a vacuum cleaner to collect dirt trapped in the weave of several rugs and sent the dirt for pollen studies. Most of the pollen matched types that one would expect to find in both Iran and Egypt. There were a few pollen types that were thought to be from plants more common to Iran than to other areas of the Middle East; however, a lack of comparative pollen samples from areas of Iran were not available for study. Thus, even though the custom agents suspected the rugs were from Iran, they did not have sufficient certainty from the pollen evidence to stop the importation of the rugs.

Example 6: The Shroud of Turin, the cloth some claim was used to wrap the body of Christ before burial, represents a high profile example where pollen data were used as a key piece of evidence in the attempt to confirm the origin of the item. During an extensive study of the Shroud, Max Frei found 49 different taxa of pollen grains trapped in the fibers of the cloth. Comparisons of the Shroud's pollen spectrum with pollen from regions of Israel and the western Mediterranean revealed similar types. Pollen types reported from the Shroud included desert-type plants that still grow in Israel. Other pollen types were similar to pollen found in nearby Turkey, and a few additional types represented plants common to the western Mediterranean region. In addition, some of the pollen (such as beech) on the Shroud were of types found mostly in central Europe. The conclusion reported by Max Frei was that the majority of the pollen he recovered from the Shroud represented plants from regions in Israel, the nearby western Mediterranean, and Turkey (Wilson, 1978). The European pollen taxa, he said, represented materials deposited on the Shroud during its display in Europe. Subsequent to Max Frei's original pollen study, the origin and suspected use of the Turin Shroud have been often questioned. More recent scientific studies by Walter C. McCrone (1997) and others cast serious doubts on the authenticity of the Shroud and on the pollen that was purportedly recovered from the Shroud.

Example 7: A person was found hanged in a barn in what appeared to be a suicide, however, police were suspicious because the hanged person had not been depressed nor had he left a suicide note. There were five people the police believed had a motive to kill the person, and each would directly profit by the victim's death; nevertheless, each suspect had an alibi. A forensic pollen analysis of the rope used to hand the victim contained pollen commonly found on a farm where vegetables were being grown. One of the five suspects owned a small truck-farm and made a living from selling a variety of vegetable crops. Although this single piece of evidence was not enough to convict any suspect, it helped police narrow their suspects to one individual. Through careful surveillance of the primary suspect, the police were able to gather enough evidence to arrest the suspect for the man's murder.

Example 8: Some years ago the Royal Ontario Museum in Toronto, Canada, was given the Gondar Hanging as a gift. The Gondar is a large, cord-woven, silk hanging of religious and artistic importance that is purported to have been made in Ethiopia during the late seventeenth or early eighteenth century. At some point after it was made, it was taken to Canada. In 1993-1994 the Gondar Hanging was restored and cleaned by the Canadian Conservation Institute. In addition to these procedures, the Royal Ontario Museum curators asked that the authenticity of the Hanging be confirmed. It was hoped that a study of the pollen trapped between the weave of the Hanging, and with the associated packing materials, might confirm its origin as being Ethiopian. Studies of the pollen contents of the Hanging revealed that many of the taxa could be traced to probable Canadian sources, as one might expect. However, a few of the pollen types recovered from the Hanging, including Justicia (water willow) and Olea chrysophylla (olive), were not from native Canadian plants, nor from plants that might have been grown as ornamentals in Canada. Both Justicia and Olea are plants that are common in the flora of Ethiopia, and can also be found growing throughout the Mediterranean and North African regions. Therefore, the pollen evidence confirmed the probable origin of the Gondar Hanging as being Ethiopian, or from a similar country in Northern Africa (Jarzen, 1994, Jarzen, 1996).

Example 9: One of the weekly British TV programs about a Scottish detective called Taggart opens at the scene of a murder in Glasgow, Scotland, where police find a man's handkerchief and a torn piece of wrapping paper containing bloodstains of the victim. The handkerchief was an inexpensive brand that could have been bought in almost any clothing store and the blood-stained wrapping paper contained no fingerprints. A forensic pollen study of the handkerchief showed that it contained Abutilon (a member of the Malvaceae family that produces showy flowers) pollen grains--a very unusual type to have been found in Scotland since the flowers are sold only by florists and it can be grown only in hot houses. After searching, police located a local Glasgow florist which regularly sold floral arrangements containing Abutilon flowers to a local pub, and police also noticed that the wrapping paper used by the florist shop to wrap the flowers matched the bloodstained paper found at the scene of the murder. After further investigation, police discovered that one of the workers at the pub had a motive for committing the murder. The suspect was arrested, and under questioning admitted that he had committed the crime and that he had used the floral wrapping paper to wipe off the axe he had used in the murder. In this example the forensic pollen evidence did not "solve" the crime. Instead, it helped the police find the florist who then linked the flowers with the pub where the murderer worked.

Illegal drugs-- Marijuana plants come in two sexes. Some plants are male and some are female. Only the male ones produce pollen. Because of the plant's archaic and inefficient method of wind-pollination, the males are among the most prolific pollen producers in nature. Because growing, harvesting, and packaging marijuana often occur in the open, marijuana pollen, as well as pollen from other local plants, will be included with any of the locally-harvested marijuana. Nevertheless, in some illegally grown stands of marijuana, male plants are weeded out because pollination and seed production are not needed. In such cases, sampling would reveal very little Cannabis pollen; a factor that might be used in court to argue that even trace amounts of marijuana pollen should be considered as significant evidence.

In a related example, the process of turning coca leaves into cocaine begins when the leaves are picked, dried in the open, processed in outdoor areas, and then refined into cocaine (Weatherford, 1987). Because most of these processed occur in or near the area where the coca plants are grown, pollen from coca and other plants in the general region are enclosed in the refined cocaine. Likewise, the first step in the production of heroin is to scar the outer surface of a poppy's immature seed pod. This scarring produces a sticky sap which is processed into heroin. Before the sap dries, it becomes an excellent trap for local pollen blowing in the wind.

Example 1: A person was arrested with a large supply of marijuana in his possession, but refused to say how or where he had obtained it. Police wanted to know if the marijuana was from some locally-grown source, or if it was imported. If it were imported, might it be part of a larger shipment linked to organized crime? A pollen analysis of the marijuana sample revealed pollen and spores that were similar to the ones found near where the suspect was arrested. Thus, it was reasoned that the marijuana sample was probably from local, home-grown sources (Stanley, 1991).

Example 2: Over the course of several weeks, three different people were arrested with fairly large quantities of marijuana in their possession. Each of the suspects was arrested in a different nearby city and each claimed that he did not know either of the other two suspects. However, an examination of the marijuana samples revealed that all three were packaged in a similar manner and might have come from the same source. A pollen analysis of each sample confirmed that all three were from a single large shipment and that the geographical origin was Southeast Asia, thus suggesting a large distribution network run by organized crime.

Example 3: Aerial photography helped police locate a large, cleared area in a national forest where marijuana was being grown. One day a nicely dressed man was seen coming out of the woods less than one mile from where the marijuana was being grown. When approached by police, the man had in his possession a small soil testing kit. In the trunk of his car, police found a small shrub that had been uprooted and placed in a bucket full of dirt. When questioned by police, the man said he had been in the woods looking for additional shrubs to plant in his yard. He said that he was using the soil testing kit to compare the pH and mineral levels of the forest soil with those in his home garden. He claimed no knowledge of the marijuana field growing nearby. Pollen analysis were conducted of dirt samples collected in the marijuana field, from the soil around the shrub in found in the man's car trunk, and from dirt in the soil testing kit. The soil from the roots of the shrub showed that it had come from some location in the forest. However, the pollen profiles from the soil found in the testing kit and from the field where the marijuana was growing were identical. This provided the needed evidence to link the suspect with the marijuana plants, and led to his conviction as the person who had cultivated the plants and was hoping to harvest them (Mildenhall, 1990).

Example 4: A shipment of 500 g of cocaine hydrochloride was seized in New York City. The cocaine was sent for forensic pollen analysis in hopes that the pollen might provide clues about the cocaine's origin and shipment route. There were three distinctly different types of pollen present in the sample. One group of pollen represented tropical plants currently growing in regions of Bolivia and Columbia. These pollen grains undoubtedly became mixed with the sample when the coca leaves were being picked and then processed to form coca paste. A second group of pollen consisted of types from jack pine and Canadian hemlock trees. Because these two trees commonly grow together only in a few regions of North America, it meant that after arriving in the United States, the cocaine must have been "cut" and then packaged in one of the following locations: a). northern Michigan or Wisconsin, b). the mountains along the Canadian border of northern New York, or c). in the mountain regions of upper New Hampshire or Maine. The third, and final group of pollen in the cocaine sample, came from weedy plants that commonly grow in vacant lots throughout downtown New York City and Manhattan Island. In summary, the pollen data showed that the cocaine originated and was processed in South America, then smuggled in to some northern area of the United States were it was probably "cut" and packaged. From there it was sent to New York City where it was probably "cut" again, and was being prepared for distribution when it was seized (Stanley, 1992).

Miscellaneous applications: There is a wide range of other materials that could serve as items for forensic pollen studies. For example, someone might suspect the origin or age of a shipment of crude oil or coal samples. Pollen and spore testing could prove useful in answering those questions. Some types of packing materials used in shipping products, such as shredded paper, straw or cardboard are also useful places to search for pollen. Commercial honey purported to have been made from the nectar of specific plant, and supposedly produced in a specific geographical location, could both be verified by pollen testing. The types of food a murder victim had eaten might be determined from the pollen and spore contents of the victim's stomach or upper intestines. The geographical origin of tea leaves, coffee beans, tobacco shipments, raw sugar, and other types of food commodities can often be determined from and examination of their pollen contents.

Example 1: A European company exported some machinery to a location in Asia. The machinery was packed in wooden crates, and during the voyage the ship stopped in a number of ports where various cargoes were loaded and unloaded. When the wooded crates reached their final destination, the company found only sacks of dirt. Investigators determined that somewhere en route the machinery had been stolen and the crated had been refilled with sacks of soil. The question was, "at which port had this occurred?" Samples of the dirt were sent to a forensic laboratory and examined for pollen. The types of pollen and spores recovered from the soil showed a geographical association with plant normally found in South Africa. One of the ports where the ship stopped was Capetown, South Africa. The pollen data enabled investigators to narrow their search for the missing machinery to one port city rather than having to investigate all of the ports of call along the ship's route. Several months later, the missing machinery was discovered in a South African warehouse.

Example 2: A shipment of Scotch whisky was shipped overseas. After it arrived, the shipment was unpacked, but only limestone rocks were present. Because both the county of shipment origin and the country of destination had ample deposits of limestone, authorities were unsure where the whisky had been illegally removed. Rumors soon spread that the whisky had been removed by local workers after it arrived at its final destination. To confirm or deny these rumors, local authorities requested that samples of the limestone be examined in hopes of discovering the source region of those rocks. The resulting analysis revealed an array of fossil palynomorphs (dinoflagellates and acritarchs) that linked the rocks to the country where the whisky had been produced, not the country where it had been sent. This forensic test proved that the whisky had been removed before the shipment had been sent, not after it had reached its final destination.

Example 3: A museum art curator needed to verify the authenticity of 10 works of art that had recently been given to the museum. To accomplish this, the curator asked that a number of tests be conducted on the paintings, one of which was forensic palynology. Pollen studies were requested because sometimes dirt and dust trapped between the picture frame and canvas contain pollen and spores that accumulate while the picture is being painted. As the painting is moved from one geographical location to another, additional pollen might become deposited. Nevertheless, traces of the originally deposited pollen should remain, unless the picture had been reframed. Therefore, if an art work is purported to be of Flemish or Dutch origin, some of the ambient pollen types from those regions should be trapped between the painting and the frame. Nevertheless, the absence of pollen from the painting's region of origin is not definitive evidence that the painting is either a fake, or that it is not from its purported origin. Reframing, or other circumstances may destroy pollen evidence of its actual origin. This study is still ongoing.

Example 4: A French antique chest was sold at auction. Later, the chest was tested to see if it was authentic. One of the tests was a forensic examination of the dirt and dust trapped inside each of the drawer's small keyholes. To accomplish this test, the lock was removed and the dirt and wood shavings trapped in the lock's corners were examined. The pollen analysis revealed none of the pollen types that one would expect to find in the region of France where the antique chest was purportedly made or used. Although the pollen evidence did not prove the antique was a fake, it created doubt and led the owner to pursue additional test, which eventually revealed that the item was indeed a fake. As in the previous example, if the locks had been changed at some point after the item had been made, the original pollen evidence would be lost.

Example 5: At the natural history museum in Marseille, France, a rare lizard had been on display for years. Information with the display stated that the lizard had been collected during a hunting expedition in New Zealand during the late 1800's. Although no living specimen of this lizard had ever been found in New Zealand, the possibility did exist that the lizard might have been captured in New Zealand and had been one of the last members of its species. A forensic pollen analysis of the dust found inside the stuffed lizard indicated it had probably been mounted in Europe. None of the pollen or spores found inside the lizard were types that would link it to New Zealand. Thus, the pollen information did not confirm, or deny, that the possible origin of the lizard was indeed New Zealand.

Example 6: Until recently the United States Department of Agriculture (USDA) supervised a federal subsidy program for the purchase of domestic honey. To qualify for participation, beekeepers had to assure the USDA that the purchased honey, under the subsidy program, was from domestic, and not imported, sources. The agency responsible for overseeing the verification of the honey subsidy program was the Office of the United States Inspector General. On more than one occasion, suspicious groups of USDA-purchased honey were sampled and analyzed for their pollen contents. Over the years of the subsidy program, the price of U.S. honey was artificially maintained at a higher price than most foreign honey. Some individuals who were seeking an illegal but quick profit, could purchase large quantities of foreign honey and then sell it under the subsidy program to the USDA as being "domestically produced honey." During one three-year testing period in the 1970's, approximately 6% of all honey samples analyzed contained tropical pollen that suggested those samples had been produced in regions of Latin America, not the United States.

Why don't we use it more often?

Forensic palynology appears to be a technique few people know about and even fewer utilize. We have searched the literature, contacted pollen specialists, and sent questionnaires to all the major law enforcement agencies and forensic laboratories in the United States, Canada, and the United Kingdom. The result of this combined study indicated that very little is know in any of these countries about forensic palynology, and that there are few palynologists who have attempted to use the technique.

The full potential of forensic palynology remains untapped and ignored in most countries, except New Zealand, where forensic palynology is widely accepted and routinely used to gather evidence in civil and criminal cases. Some of the reasons why forensic palynology is not more widely used might be a result of some or all of the problems listed below.

Specialists: Even if law enforcement authorities want to use forensic palynology, they might have a problem finding someone who would be willing to examine forensic samples. There are few pollen analysts in the world who have had forensic training or experience; there are even fewer who might be willing to work on forensic pollen samples.

One concern, in some countries such as the United States, is personal liability if asked to testify in court. A second concern is the potential of having to submit to cross-examination in court. Often, cross-examination can be a devastating experience for a scientist who may not be accustomed to having his or her personal life, education, research methods, or scientific expertise drawn into question, or told that the data he or she might have presented is irrelevant or inadmissible because of some minor technicality. Contrary to what a scientist may believe, a court is not where one arrives at the truth. Instead, the sole purpose of court testimony is to ensure that the prosecution has prepared an "airtight" case, has established their case "beyond a reasonable doubt," and that the rights of the defendant have not been compromised. Third, many scientists may not be able, or willing, to commit the time needed to research the background of a case, or to complete the needed forensic testing within a limited time frame.

Samples: Sample collection is also a major concern. Forensic pollen samples that are collected improperly, or are contaminated after collection, are of minimal value. This is one reason we recommend law enforcement agencies seek the advice of a skilled forensic palynologist before as well as after forensic samples are collected. No forensic palynologist wants to waste his/her time examining samples that cannot be used as evidence because of improper collection procedures or post-collection contamination. In some cases, of equal concern for the forensic palynologist is not being able to assure the court, during testimony, that he or she is "certain" that no possible opportunity for contamination may have occurred prior to the time they received the sample.

Facilities: Many palynologists are not equipped to conduct forensic work. They may not have access to a contamination-free laboratory facility, or they may not have the special type of equipment that is needed in processing samples. Also, some palynologists may not have top-quality optical microscopes, or access to scanning electron microscopes, should they be needed. Finally, to prevent accusations that a sample may have been mixed during processing or mislabeled, often elaborate steps, requiring at least two individuals present, must be taken at every step of an analysis in order to ensure that such accidents did not occur.

Yet another concern is access to pollen and spore reference collections. Because there are hundreds or even thousands of potential plant taxa that could exist in any forensic sample, precise identification of pollen types is often time-consuming. Although many palynologists have access to some pollen and spore reference collections, not all palynologists have access to vast collections that encompass a broad range of pollen types found in many different regions of the world.

Funding: Funding for forensic work is a major concern. Although some forensic palynologists are employed by state, provincial, or federal agencies, and may be able to conduct a few forensic studies free of charge, most cannot.

This concept of the "user" being asked to pay for pollen analyses is not something that all law enforcement personnel expect. Furthermore, by the time that many personnel realize the potential benefit of conducting forensic pollen studies, analysis money is spent. This lack of funding for analyses, combined with the realization that most pollen laboratories are underfunded, means that some important samples cannot be examined. Like many others, both authors have often done forensic samples "for free", but we are also under heavy pressure to support the upkeep of the laboratory, the purchase of equipment and chemicals and the salaries of the personnel with outside funding.

Summary

Forensic palynology is in its infancy. It remains untried in many regions of the world, is seldom used in other regions, and is not yet accepted or recognized as being valuable evidence in most court systems. There are also still misconceptions about what types of information forensic pollen samples can provide. Often police and other investigators regard forensic samples, and the testing results, only as tools that can be used to "convict" a suspect.

Often, many types of forensic data, such as pollen results, do not actually "convict" a suspect. Instead, the samples are useful tools that can point investigators in the "right" direction, or narrow the number of suspects, or perhaps even eliminate a person as a prime suspect. Nevertheless, even in this type of supporting role, forensic palynology can become a powerful tool of the forensic scientist.

We believe that the next decade will become a "trial" period for forensic palynology. It has already become widely accepted and court-tested in countries such as New Zealand, but this type of acceptance has yet to be recognized in regions such as the United States and elsewhere.

References Cited:

  1. Brown, G. and Llewellyn, P., Traces of Guilt: Science fights Crime in New Zealand. Collins Publishers, Aukland, New Zealand. 1991.
  2. Bryant, V.M. Jr., Pollen: Nature's Fingerprints of Plants. 1990 Yearbook of Science and the Future, Encyclopedia Britannica, Chicago, Illinois. 1989. pp.92-111.
  3. Bryant, V.M. Jr., Mildenhall, D.C., and Jones, J.G., Forensic palynology in the United States of America, Palynology, 1990, 14. pp. 193-208.
  4. Erdtman, G., Handbook of Palynology. Hafner Publishing Co., New York. 1969.
  5. Faegri, K., Iverson, J., and Krzywinski, K., Textbook of Pollen Analysis, 4th Edition, John Wiley & Sons, New York. 1989.
  6. Jarzen, D., Palynological analysis of the Gondar (Ethiopia) Hanging. Program Abstracts, 27th Annual Meeting of the American Association of Stratigraphic Palynologists: 20. 1994.
  7. Mildenhall, D.C., Forensic palynology. Geological Society of New Zealand Newsletter, 58(25), 1982.
  8. Mildenhall, D.C., Deer velvet and palynology: and example of the use of forensic palynology in New Zealand. Tuatara, 30, pp. 1-11, 1988.
  9. Mildenhall, D.C., Forensic palynology in New Zealand, Review of Palaeobotony and Palynology, 64-65, pp. 227-234, 1990.
  10. Mildenhall, D.C., Pollen plays part in crime-busting. Forensic Focus, 11, pp. 1-4, 1992.
  11. Newman, C., Pollen: breath of life and sneezes, National Geographic Magazine, 166(4), pp. 490-521, 1984.
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  13. Pain, S., Silent witnesses, Kew, (Autumn), pp. 22-25, 1993.
  14. Pearson, R., Probable Cause, St. Martins Paperbacks, New York, 1991.
  15. Skinner, D.B., et al., Of Rainbow Warriors, deer antlers, platinum, and other things: forensic science in New Zealand, New Zealand Geological Survey Report, G-130, 1988.
  16. Stanley, E.A., Forensic Palynology, Proceedings of the International Symposium on the Forensic Aspects of Trace Evidence, USDOJ, pp. 17-30, 1991.
  17. Stanley, E.A., Application of palynology to establish the provenance and travel history of illicit drugs, Microscope, 40, pp. 149-152, 1992.
  18. Tauber, H., Differential pollen dispersion and filtration, In: Qutaternary Paleoecology, Yale University Press, New Haven, pp. 131-141, 1967.
  19. Weatherford, J.M., Cocaine and the economic deterioration of Bolivia, In: Conformity and Conflict, Little, Brown and Co., Boston, pp. 412-423, 1987.
  20. Wilson, I., The Turin Shroud, Penguin Books, London, 1978.
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