A young man with no history of violence was likely experiencing magic mushroom-induced psychosis and delusions when he broke in and attacked a senior Calgary professor in her home, according to a doctor who specializes in forensic toxicology.

Matthew Brown, 28, is on trial for breaking and entering and assault with a weapon following a bizarre, violent incident on Jan. 13, 2018.

Mount Royal University professor Janet Hamnett, 68, suffered several injuries including a broken hand when she was beaten with a broom handle by Brown, who had entered her bedroom around 4:30 a.m. after smashing through her sliding glass doors.

Brown testified last week, and although he said he had no memory of the attack, he offered a tearful apology to his victim and her family.

In his testimony, Brown said that while drinking with friends, he estimated he consumed about 2.5 grams of mushrooms — the doctor estimated it was around 4.5 grams.

'Lost touch with reality'

Earlier in the trial, Brown's friend testified that around 4:30 a.m., he appeared at the door of the home and then "ran into the night."

On Tuesday, defence lawyer Sean Fagan called Dr. Mark Yarema to testify.

Yarema said he was of the opinion that Brown had "lost touch with reality" the night of the attack.

"My opinion is that what he had likely experienced was an episode of delirium where he was unaware of his surroundings and where he may have experienced delusions and hallucinations," said Yarema.

Someone in touch with reality, said the doctor, "would not be expected to stand naked in a house, run naked through the Springbank Hill neighbourhood, break into homes and injure people."

Yarema used medical records, information from police, letters from Brown's friends and family, a summary of the facts of the case and the medical opinion of a psychologist who was also involved in the case.

According to the doctor, a person experiencing delirium — an altered level of consciousness — would not have control over their actions. They would not be aware of their name, birthday, address or even where they were. They would not be able to follow basic instructions.

Because magic mushrooms contain psilocybin, which is structurally similar to serotonin, people also lose the ability to make judgments on what is right and what is wrong and whether to do something or not do something, said Yarema.

A unique defence

Fagan is arguing his client was intoxicated to the point of automatism, meaning the defence is Brown was too high on magic mushrooms to understand his actions at the time of the attack.

Normally that defence is not permitted, but in a hearing held ahead of the trial, Brown's lawyer successfully argued the current law is a violation of his client's Charter rights.

Recreational users of magic mushrooms can cause people to see colours more vividly, experience a loss of inhibitions, feel more relaxed and feel heightened sensation.

The effects last four to six hours but can take as long as 12 hours to wear off.

Coincidentally, Brown was a student at MRU and captained its hockey team for three years.

Court of Queen's Bench Justice Michele Hollins will hear from one more medical expert called by the defence before lawyers move into closing arguments later this week.