Operation Trace was set up by former Garda Commissioner Pat Byrne in 1998 to investigate the disappearance of six young women in the Leinster area between 1993 and 1998.
A special investigation unit at Naas Garda Station was set up to determine whether a serial killer was responsible for the disappearance of the women -- Fiona Sinnott (19), Fiona Pender (25), Ciara Breen (18), Annie McCarrick (26), Jo Jo Dullard (21) and Deirdre Jacob (19).
Two FBI agents were drafted in to assist it in the operation and the garda's cold case unit, the National Bureau of Criminal Investigations (NBCI), to examine their files on unsolved murders and the missing women.
They specialise in profiling serial killers and rapists.
Jailed rapist Larry Murphy has emerged as the only prime suspect in the women's disappearances. The FBI agents concluded that the modus operandi and profile of the unknown suspect fitted Larry Murphy in three of the cases.
Their profile for the killer of the three missing Leinster women points to a married man in his late 30s who has children and no police record. Larry Murphy fits all the criteria.
Murphy has been effectively ruled out of involvement in the cases of Ciara Breen, Fiona Pender and Fiona Sinnott, but gardai believe he kidnapped and murdered the other three women.
The Trace detectives discovered that Murphy had been roofing a house in Newbridge around the time Deirdre Jacob went missing.
His route home from this job took him right past her house in Roseberry, Newbridge, and along the roadway where she was last spotted at 3.30pm on Tuesday, July 28, 1998.
His only link with the disappearance of Jo Jo Dullard and Murphy was the geographical closeness of where Jo Jo disappeared and where Murphy attacked a Carlow businesswoman in 1999
Jo Jo was last seen at a public telephone box in the village of Moone, just five miles from where Murphy lived in 1995. Detectives have interviewed Murphy on three occasions about the missing women but he has refused to co-operate.
Operation Trace has so far not produced any concrete evidence. Detectives have found no link between Murphy and any other of the disappearances despite in-depth enquiries and searches of his home and surrounding land.
Annie McCarrick was the first of the women to vanish following a day trip to the Wicklow Mountains in March, 1993. She was last seen with a "strange man" in Johnnie Fox's pub.
On August 22, 1996, part-time model Fiona Pender vanished from her apartment in Tullamore. She was seven months pregnant and had spent the previous day shopping for baby clothes in Tullamore.
Ciara Breen went missing from her home in Bachelors Walk, Dundalk, on February 13, 1997. It is thought she left her home for a pre-arranged meeting with an unknown person.
Fiona Sinnott, from Bridgetown, Co Wexford, has been missing since February 9, 1998. There have to date been no verified sightings of her since she left the pub, Butlers of Broadway, with her boyfriend that night.