A knife and clothing found in the same truck as a man accused of killing a southern Alberta family were stained with the blood of victims, an RCMP expert testified on Thursday.

Blood on the knife found in the truck was the same as that of the slain father, according to testimony Thursday from Robert Schimpf, a molecular genetics expert based at the RCMP's forensic lab in Edmonton.

Schimpf called it a "one-in-170-trillion match."

Jeremy Steinke, 25, is charged with three counts of first-degree murder in the 2006 stabbing deaths of a couple and their son, 8, in their Medicine Hat home.

The Crown is trying to prove that Steinke plotted with his girlfriend, then 12, to kill her family and run away together.

Members of the slain family can't be named to protect the identity of the daughter under the Youth Criminal Justice Act.

Authorities located Steinke and the girl in a Mazda B4000 pickup truck in Leader, Sask., the day after the slayings.

A bag of Steinke's clothing found in that same truck yielded a number of other DNA matches, said Schimpf. The victims' blood was found on some jeans, shoes, a hooded sweatshirt, and bandana, while both the father's blood and Steinke's blood were also detected on a mask.

In one sample, DNA from a blood stain came from the eight-year-old boy. The chance of finding another person with that same DNA is one in 510 trillion, said Schimpf.

The DNA expert also said that two knives found inside the house had the boy's blood on one of the blades and the dad's on the other.

The girl, who was found guilty last year of three counts of first-degree murder, is serving a maximum 10-year sentence for young offenders.

If convicted, Steinke faces a life sentence with a minimum of 25 years in prison.

With files from Bryan Labby, Scott Dippel