In Depth
Robert William Pickton
Forensic Science: Its role in the missing women investigation
January 17, 2007
CBC News
Ten acres is a lot of ground to cover with a fine-toothed comb. But that's essentially what teams of investigators are doing in Port Coquitlam, B.C.
They are trying to find any tiny piece of evidence – bone fragments (bone slivers, even), hair, joints, teeth – anything that might contain a few cells, enough for a usable sample of DNA.
But the size of sample that’s needed to be usable has shrunk, even in the last few years.
"A blood sample – a dot of an 'i' from 10-point type – would easily be recoverable as DNA," says Kevin McElfresh, senior vice-president of the BODE technology group in Virginia, a DNA lab the RCMP has used in several cases.
McElfresh says cigarette butts, hairs and small bone fragments could sometimes yield DNA samples a few years ago, but it was hit and miss.
"Now, cigarette butts are a ton of DNA. Not a problem," he says.
"We can get DNA from the tags of shirts that people have been wearing, not even bloody," McElfresh says.
The ability to find DNA in such tiny fragments also has its drawbacks, though.
When police told Maggie deVries that her sister Sarah's DNA had been found on Robert Pickton's pig farm, they pointed out that it wasn't enough evidence to lay charges against him.
"(The DNA) doesn't even really prove that Sarah was ever there," said deVries. "It just proves something she touched was there."
Teeth are a great source of DNA, for one reason.
"That nice hard covering on the outside of the tooth, protecting the inside pulp," says McElfresh. "You can go inside and recover that and do a very nice DNA test."
Sometimes there's no pulp left in the tooth because a root canal removed it. In those cases, freezing the tooth in liquid nitrogen and smashing it produces a fine powder, rich in DNA.
However, because teeth are so resilient, they are sometimes all that remains of a murder victim.
"Sometimes, you try to split the tooth open so it can be put back together, so there's some semblance of that tooth to return to the family," says McElfresh.
Investigators found 3,000 pieces of evidence in the top levels of the dirt on the farm.
To continue their searches, though, police brought in heavy excavation equipment to sift through the soil, including two 50-foot flat conveyer belts and two dump trucks.
The investigation team is made up of 91 people: 30 to 40 police and 52 forensic and archeological experts. Several archaological students were hired to help go through the dirt as it passes by on the conveyer belts and identify remains.
In June, police estimated that the excavation could take a year. In September, they said the investigation will go on indefinitely.
"If these activities go back to, say, 1995, seven years ago, some of (the victims) could be buried fairly deep," says former Vancouver police officer Kim Rossmo, an expert in serial killers.
"Now, one factor to the benefit of the police is criminals are lazy, so they're not going to be 40 feet below the surface," says Rossmo.
Other forensic experts will focus on reconstructing the crime scene by looking at how the bones were scattered around the farm.
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