A woman's skull found 12 years ago near a British Columbia highway was cut the same way as remains found on Robert William Pickton's farm, a police officer testified at Pickton's trial Monday.

Sgt. Timothy Sleigh said the skull found near the highway of the unidentified woman, known only as Jane Doe, appeared to have been bisected with a saw.

The remains of three of the women Pickton is accused of killing — Mona Wilson, Andrea Joesbury and Sereena Abotsway — were found in a similar state on Pickton's pig farm in Port Coquitlam, B.C. in 2002.

Sleigh said in all his years as a crime scene investigator, he had never seen remains in this state.

"The Mona Wilson exhibit appears similar to Andrea Joesbury and Sereena Abotsway and the Jane Doe exhibit," Sleigh said in court, according to the CBC's Natalie Clancy.

A man found Jane Doe's skull in 1995 on a creek bed in Mission, B.C.

Sleigh said he investigated and obtained a DNA profile of the dead woman, but never figured out who she was. He testified he thought nothing more of the Jane Doe case until he attended the autopsy of the remains of Abotsway.

When Sleigh realized the remains of all four women were similar, he said he ordered investigators to review the Jane Doe case.

The jury at the Pickton trial has heard that police discovered two human bones on Pickton's property that matched the DNA profile of Jane Doe.

Pickton is charged with the first-degree murders of Wilson, Joesbury and Abotsway, as well as Brenda Wolfe, Marnie Frey and Georgina Papin. All six disappeared from Vancouver's Downtown Eastside.

During the cross-examination by defence lawyer Adrian Brooks on Monday, Sleigh admitted that there were 80 instances where an investigator's DNA or a lab technician's DNA ended up on the exhibits being studied.

But Sleigh also testified that there were 600,000 exhibits in the case, and officers were very careful not to contaminate evidence.

Other exhibits found near social club

Sleigh also testified about exhibits found near a social club run by Pickton's brother, David.

Sleigh said police found women's clothing, shoes, syringes and condoms in vehicles near the club, called Piggy's Palace.

One vehicle was tampered with before police examined it, Sleigh said. He said security had to be increased after police tarps were disturbed.

Sleigh said there are still exhibits from the property that have yet to be examined by a crime lab.

Sleigh is the 14th witness to take the stand in Pickton's trial.