The lawyer for François Pépin, the man accused of killing Laval policewoman Valérie Gignac in 2005, plans to argue his client was suffering from a mental disorder at the time.

Montreal lawyer Robert La Haye said the issue is not whether Pépin killed Gignac, but what state of mind he was in at the time. The officer was shot point-blank through the apartment door with a rifle while she was responding to a domestic disturbance call at Pépin's apartment in December 2005.

La Haye told CBC News during an interview Thursday that when Pépin goes to court in the fall, he will ask the jury to determine whether his client was mentally stable.

"We will admit the facts: it won't be contested," he said. "After the Crown's case, we'll present our defence with psychiatrists, with experts that will explain that, at the time of the incident, with regards to his state of mind, he was suffering from a mental disorder that renders him irresponsible."

LaHaye laid out his strategy after a Quebec judge determined on Tuesday there was enough evidence to proceed with Pépin's court case.

"He could not appreciate the nature and quality of his acts, or knowing that it was wrong," La Haye told CBC News. "He understands what is a trial, he can help his lawyer, and he can answer questions. But at the time of the crisis, he was in a crisis, and he was mentally disassociated."

Gignac was the first Laval police officer to be killed in the line of duty.

Pépin has been held at a detention centre in St-Jérome since the shooting almost two years ago. He will return to court on Sept. 6.