Catherine Birnie -- Australia

David BIRNIE and his wife Catherine BIRNIE abducted, drugged, raped, 
photographed and murdered three women and a teenage girl. Denise BROWN, 
Mary NEILSON, Susannah CANDY and Noelene PATTERSON were murdered during 
October and November 1986 after being held captive at the BIRNIE's 
Perth home for days. A fifth victim managed to escape and raised the 
alarm. After a lengthy interview David BIRNIE led police to the graves 
of the four women. They are also suspected of murdering four other 
missing Perth women. They were also friends with Queenslander Barrie WATTS, 
who was convicted of the 1987 murder of 12 year old schoolgirl, Sian KING. 
Both defendants were sentenced to life imprisonment.  

http://www.redbackwebs.com.au/cufflinks/police/serial.html#Birnie

http://www.crimelibrary.com/serial8/birnies/

http://www.crimetime.co.uk/features/carolannedavis2.html