A blood-stained tank top seized from Christopher Alexander Falconer’s car contained DNA likely belonging to Amber Kirwan, a DNA expert testified Thursday.

Thomas Suzanski, an RCMP DNA expert with 20 years of experience, is the latest witness to testify in the first-degree murder trial at the Nova Scotia Supreme Court in Pictou.

Suzanski began his testimony with a PowerPoint presentation, explaining the basics of DNA and how it is tested during crime investigations.

He told the court that only twins have identical DNA, and that when two people are involved in a crime scenario, there is an exchange of DNA between them.

“It’s the strongest type of evidence we have,” he said.

Testimony heard earlier in the trial stated that Kirwan disappeared in the early morning hours of Oct. 9, 2011 after spending a night out with friends at Dooly’s pool hall and Bar in New Glasgow.

The 19-year-old was last seen leaving Dooly’s and heading for Big Al’s convenience store located just up the street.

Kirwan’s boyfriend, Mason Campbell, testified last week that she was supposed to meet him at Big Al’s but she never showed up.

Kirwan’s partly-decomposed body was found in a shallow grave off a logging road in Heathbell, N.S. on Nov. 5, 2011. Kirwan was found naked, her wrists bound with a shirt and a towel.

Falconer, 31, is charged with first-degree murder in her death. He has pleaded not guilty.

Suzanski testified on Thursday that a tank top seized from Falconer’s vehicle tested positive for DNA likely belonging to both Falconer and Kirwan. He said the tank top was tested on four different occasions.

The court heard that the odds that two of the five samples taken from the tank top were not from Kirwan were one in 1.14 billion.

The odds that one of the samples taken from the shirt was not from Falconer were also one in 1.14 trillion, the court heard.

A third DNA sample on the shirt belongs to neither Falconer, nor Kirwan, according to the expert.

Defence Taylor Mike Taylor said that is significant.

“Obviously the Crown wants the jury to draw the inference that Mr. Falconer was in contact with that tank top at the relevant time, but it’s pretty clear that there’s other DNA on that tank top that could lead to the conclusion that someone else was involved,” said Taylor.

The Crown attorneys said Suzanski explained how other DNA could have ended up on the tank top.

“He spoke on a number of occasions regarding the mechanism or mechanics of DNA transfer and I think that really answers your question in terms of how one might find multiple profiles on a particular item or article of clothing,” said Crown prosecutor Bill Gorman.

Suzanski testified that several items seized from a camper belonging to Alice Meier, Falconer’s stepsister, also tested positive for Kirwan’s DNA.

The camper is located on the Hardwood Hill Road, about 2 km from where Kirwan’s body was found. Falconer’s father also lives in the area, the court heard.

Items seized from the camper that match Kirwan’s DNA include a piece of black cloth found beside the bed, hair found on the headboard, and hair found on a piece of duct tape on the floor.

Suzanski testified that DNA testing was done on a knife belonging to Falconer but there wasn’t enough DNA on the knife to conduct a reliable test, and the tests were inconclusive.

The court heard that DNA belonging to Kirwan’s boyfriend wasn’t found on any items seized from the camper.

During cross-examination, Suzanski agreed with Taylor that Falconer’s DNA was not found in samples taken from the trailer.

The trial opened with testimony from Deno Miller, who knows Falconer’s stepsister, on Thursday.

Miller testified that he spent the 2011 Thanksgiving weekend – the same weekend Kirwan disappeared – at his girlfriend’s cottage in Caribou Island, N.S.

Miller said Alice Meier arrived at the cottage with her boyfriend and two children the afternoon of Oct. 8. They spent the night and Miller testified that Meier called Falconer to bring them some more beer on Oct. 9.

The court heard that Falconer arrived with a case of beer around 1 p.m. that day and stayed for about a half an hour. He had another man with him but Miller said he didn’t know, or didn’t remember, who the man was.

Miller said it was the first time he ever met Falconer and he never saw him again.

Meier, her boyfriend and children left the cottage later that day.

With files from CTV Atlantic's Dan MacIntosh