Jacques Delisle, a retired judge at the Quebec Superior Court, is accused of shooting his wife in the head with a revolver.
He maintains that his wife, who was paralyzed on half her body, committed suicide.
In Wednesday's testimony, the police officer who responded to the 911 call said the ex-judge had asked that his wife's wish to die be respected and that no resuscitation attempt be made.
"He warned the ambulance workers not to work on his wife because these were her last wishes," said Jean-François Begin, a Quebec City police officer.
The death of Marie-Nicole Rainville, 71, is considered to be the first time a Canadian judge faces such serious charges.
On the first day of the trial, the court heard that Delisle had a mistress with whom he had expressed some desire to start a life. There was also a police statement that gun-powder residue found in Rainville's hand was located deep in the palm, a strange location for someone who had used the gun on herself.
On Wednesday, the second day of hearings, the trial heard about the request to ambulance workers. It also heard that Delisle voiced the same desire to a nurse at the hospital.
Several minutes after the chat with the nurse, a doctor announced Rainville's death.