The defence team for accused triple-killer Ian Bush closed their case Tuesday after less than two days of evidence from three witnesses.

Bush is facing three counts of first-degree murder in the June 2007 deaths of retired Tax Court of Canada judge Alban Garon, 77, Garon's 73-year-old wife Raymonde, and their friend and neighbour Marie-Claire Beniskos, 78.

Bush, now 61, was charged in 2015 and has pleaded not guilty.

The trial will resume Monday with closing statements from the defence and the Crown, whose case took about a month to present and wrapped last week.

After closing statements Monday, Justice Colin McKinnon will give instructions to the jury before they begin deliberating.

Case centres on DNA evidence

The climax of Tuesday's testimony came as Crown attorney James Cavanagh cross-examined the defence's final witness, Cecilia Hageman, a DNA expert who worked at the Centre of Forensic Sciences from 1991 to 2013.

Raymonde Garon Alban Garon Marie-Claire Beniskos triple homicide June 2007 victims

From left, Raymonde Garon, her husband Alban Garon, and their friend and neighbour Marie-Claire Beniskos were found dead in the Garons' condo in June 2007. (Photo collage by CBC)

She had spent much of the day testifying about the two pieces of DNA evidence central to the case: a body hair found near the bodies of the victims in the living room of the Garons' condo — a hair which did in fact belong to Bush, he has admitted — and a smear of blood, also found near the bodies.

Court has heard that Alban Garon can't be excluded as the source of the major DNA profile found in the blood mixture, and that Bush and a Toronto man can't be excluded as the sources of a minor, incomplete DNA profile found in the same blood sample. The Toronto man was later eliminated as a suspect by police.

The probability that a randomly selected person unrelated to Bush would coincidentally share the same DNA in the minor profile is estimated to be one in 13,000.

Dramatic recap of Crown allegations

As the cross-examination came to a close Cavanagh dramatically recapped the Crown's allegations: that Bush, identified on surveillance video by his own three children and his former partner, got inside the Garons' condo, forced all three victims to the ground where he bound them, breaking some of their bones in the process, pulled plastic bags over their heads, and grabbed an iron bar from a bag he had brought to beat one victim so severely that blood poured from the head wound. The blood spilled out of the ripped bag and onto Bush, then the floor, Cavanagh said.

Cavanagh asked Hageman whether that scenario would adequately explain why the full DNA profile in Bush's body hair and the partial DNA profile in the mixed blood was found near the bodies.

"I can't speak to the events described," Hageman replied, but if Alban Garon's blood got onto Bush and then dripped to the floor, that would make it possible for some of Bush's DNA, in the form of skin cells, to show up in the test results.

Hageman told court she couldn't exclude that possibility.

Re-examination by lead defence lawyer Geraldine Castle-Trudel was brief.

Using the random match probability of one in 13,000, Hageman testified that in the City of Ottawa, which has about one million residents, somewhere between 90 and 100 people could also match the minor, incomplete DNA profile found in the mixed sample of blood. In Canada, with about 35 million residents, the number would climb to more than 1,000.

Blood sample less discriminating

Hageman, now a university professor, was called by Castle-Trudel to give a letter of opinion about the two pieces of DNA evidence.

She testified during examination in chief earlier Tuesday that she performed administrative reviews on the conclusions reached by lead forensic biologist Brian Peck, who testified earlier in the trial. She told court she agreed with Peck's findings and found no problem with his reports.

Hageman told court, as Peck did, that the DNA result from the mixed blood wasn't as discriminating as the hair result.

As for their proximity to each other, she said she "cannot exclude that minor [blood] profile as coming from the same person as the hair." It's one of two possibilities, the other being that they come from different people.

It wouldn't matter if the two pieces of DNA were found "two centimetres apart, 20 centimetres apart, or two rooms apart," she told court. She can only examine the random match probability as calculated to determine possible sources.

More than 1 contributor?

Hageman was also asked by Castle-Trudel about the assumption made during DNA analysis of the mixed blood that the minor profile came from one person.

Hageman made it clear, as Peck did, that the assumption was a reasonable one to make based on the amount of DNA present, and allowed for further analysis.

If the assumption were made that the minor profile came from more than one person, no further testing would have been done because there would be no way, with a profile so incomplete, to determine which bits of DNA came from which person, she told court.

At the same time, the lone contributor scenario isn't the only one out there, Hageman testified. It remains a possibility that it came from two different people.

Witness changed letter

Hageman repeated several times that, because of the missing data in the partial DNA profile, one cannot say unequivocally that there is only one contributor.

It remains an assumption, and a reasonable assumption at that, but not a conclusion, she testified.

Cavanagh pointed out that Hageman submitted several letters of opinion to the defence team, and that the final version presented to the jury Monday — written on May 1, 2017 — had been changed to exclude a section about the DNA of the Toronto man not matching the DNA found in the body hair.

Hageman told court that yes, the defence had asked her to remove the line and replace it, and so she did so. She testified that she relies on her clients to "focus her on what is at issue."

Closing arguments in the trial are expected Monday.