HALIFAX - A psychiatrist says it's possible Christopher Garnier was suffering from a condition in which he was not fully aware of his actions immediately following the death of off-duty police officer Catherine Campbell.

Dr. Stephen Hucker was hired by the defence to prepare a report ahead of Garnier's murder trial, and he has been qualified as an expert witness in the Nova Scotia Supreme Court in Halifax.

Defence lawyer Joel Pink asked Hucker today about "automatism," and he said that in psychiatry, it is defined as behaviour that a person is not consciously aware of.

Hucker says it's possible the Halifax man was in a state of automatism after Campbell's death on Sept. 11, 2015.

He previously testified that Garnier suffered from acute stress disorder following her death, which could explain why he had fragmented memories about what happened to Campbell.

Under cross-examination by Crown attorney Carla Ball, Hucker agreed he never mentioned automatism in his report and he agreed that it is a rare psychological condition.

Garnier has pleaded not guilty to second-degree murder and interfering with a dead body.