Unidentified DNA was found on the teeth of two women Robert William Pickton is accused of killing, a B.C. court was told Thursday.

DNA expert David Morissette testified about three teeth from Sereena Abotsway and two from Andrea Joesbury that had been taken from their remains found in buckets on Pickton's farm in Port Coquitlam.

Unidentified DNA was found on one of Joesbury's teeth, Morissette told Pickton's murder trial in a New Westminister court. He also said unidentified DNA was found on one tooth belonging to Abotsway.

But Pickton's DNA was excluded as a match on four of the teeth. One of Joesbury's teeth didn't have enough DNA to compare it to other samples.

Morissette testified forensic experts went through a number of steps to try to identify the DNA. They compared the results to databases that included investigators, lab examiners and anyone associated with the farm, but were still not able to find a match.

He also spent a great deal of time trying to examine lab procedures and the possibility of contamination

"At the end of the day, I don't know where these profiles came from," he said. "We'd looked into it in as great detail as we possibly could and came to no conclusion."

Morissette also testified that on one of Abotsway's teeth, two profiles besides hers surfaced. A man and a woman known to have visited Pickton's farm couldn't be ruled out as being matched to the DNA.

Pickton is charged with six counts of first-degree murder in the deaths of Abotsway, Joesbury, Mona Wilson, Marnie Frey, Georgina Papin and Brenda Wolfe, among missing women from Vancouver's Downtown Eastside. In all, Pickton is accused in the deaths of 26 women. He has pleaded not guilty to all charges.

The issue of lab contamination was also raised, this time by the Crown.

Reporting officer Kathleen Horley testified 136 of the 235,398 samples processed for DNA were contaminated. Of those, 45 were contaminated by lab staff, 45 by investigators, 35 by controls used to test the process and 14 were unknown.

Pickton has been in custody since February 2002, when police descended on his farm and began a massive investigation that led to the murder charges against him.

With files from the Canadian Press