A forensic entomologist took the stand at the trial of Christopher McDonald in the 2008 murder of 29-year-old Corinne Burns in Guelph.

Sherah Van Laerhoven, the academic chair of the Forensic Science Programs at the University of Windsor, is one of only 13 forensic entomologists in North America and only two in Canada.

She testified about insect samples she received 15 hours after they were collected from Burns' body.

Working backwards, Van Laerhoven said based on those samples she was able to determine the eggs were laid the afternoon of May 25.

She said that in her opinion, that would put the time of death sometime before 2 p.m. on May 25, 2008.

Burns' naked body was found two days later, on May 27, 2008, in Guelph's Norm Jary Park.

The defence argued police did not properly monitor the temperature of the Styrofoam box where the insects were being kept while it was transported from the crime scene to the police station and then driven to the lab in Windsor.

Defence lawyer Angela McLeod said "Other than the temperature taken at the scene, no one took or recorded temperatures for almost 15 hour.s…and that seriously undermines the entomologist from our stance." 

The defence also says determining the time of death does not prove Burns was murdered.

"We take the position she was not killed, she died from a drug overdose."

McDonald, 38, has pleaded not guilty to first degree murder and aggravated sexual assault.

Both sides are expected to wrap up their cases by Wednesday, though the defence has not yet decided if McDonald will take the stand.

Closing arguments are expected next Tuesday and a verdict is possible before the end of next week.

Another high profile case

Van Laerhoven has testified in other high profile cases, including the Ontario Court of Appeal review that led to the exhoneration of Steven Truscott in 2007.

Truscott had been convicted in the 1959 murder of 12-year-old Lynne Harper.

But Van Laerhoven recreated the scene and found Harper died earlier than originally thought, helping rule out Truscott as the killer.