An expert forensic psychiatrist says Darryl Sheepway’s mental state was “abnormal” when he shot and killed Christopher Brisson in August 2015.

Dr. Shabehram Lohrasbe testified in Sheepway’s defence Wednesday in Yukon Supreme Court.

Sheepway is on trial facing a first-degree murder charge in Brisson’s death.

Lohrasbe explained to the court how crack cocaine intoxication and addiction can impact mental effects.

But he stressed that his findings in Sheepway’s case were purely from a psychiatric rather than legal perspective.

Lohrasbe said that crack cocaine causes people to get high very quickly and then crash very quickly.

And experiencing these jagged highs and lows can lead users to be irritated and edgy.

“It’s a very disorienting experience, normality starts to fall away,” Lohrasbe said.

When users crash, he added, they experience changes in blood pressure, heart rate and temperature, and feel jittery and “not right.”

Because the lows are lower than normal, he said, users are often “frantic” to get more of the drug.

“People don’t want to believe they are going down this hole of despair but know they are,” he said.

Other effects from crack cocaine use include focusing on the drug while everything else, including caring about values and consequences, is tuned out.

“It’s a mindset where you are disconnected from the many realities of your normal life. It frames how you see things,” Lohrasbe said. “It hijacks awareness essentially.”

Users can also be hyperreactive where they respond impulsively and excessively to stimuli.

Lohrasbe said Sheepway was experiencing these symptoms along with being chronically sleep-deprived when he met Brisson on the McLean Lake Road on Aug. 28, 2015.

Sheepway testified that he was planning to rob Brisson for drugs using his shotgun. He claimed that he expected Brisson to comply when he pointed the shotgun at him, but Brisson grabbed the gun and they struggled over it.

Lohrasbe testified that Sheepway would have hyperreacted to that unexpected event.

Sheepway likely would not have insight nor grasp consequences at the time, Lohrasbe added.

But he said that while Sheepway’s mental state was abnormal, he was not experiencing the psychotic symptoms that can result from excessive cocaine use.

During cross-examination, Crown prosecutor Leo Lane noted that Sheepway made rational, goal-oriented decisions before and after Brisson’s death.

This included planning the robbery and later getting rid of evidence.

Lohrasbe testified that goal-directed behaviour can co-exist with “grossly abnormal” mental states.

He added that according to Sheepway, he had become very skilled in maintaining a “facade of normality” to hide his drug use.

Lohrasbe also said that a major event like Brisson’s death could have caused Sheepway to become more clear and coherent.

“It’s like a slap in the face; wake up,” he said.

Lohrasbe conceded that his findings were largely based on Sheepway’s claims about his drug use and what happened on the McLean Lake Road.

He said there was no way to be certain about Sheepway’s level of intoxication nor how much crack cocaine he used that day.

“I think it’s a reasonable assumption that that was what was going on but I’m in no way saying it was a certainty,” Lohrasbe said of his findings.

Crown prosecutors hope to call forensic psychiatrist Dr. Phillip Klassen to provide rebuttal evidence.

A hearing that will decide whether his evidence is admissible will be scheduled later today.

Justice Leigh Gower is hearing the case.