In response to a query about what effect a combination of Temazepam, Benadryl and alcohol could have on a person suffering from paranoid psychosis, Watts replied it did not necessarily have a direct impact on psychotic symptoms or hallucinations.
The jury has previously heard that the sleep drug Temazepam and Benadryl, an over-the-counter allergy medication, were found in the body of Jun Lin, the man Magnotta killed and dismembered in May 2012.
“Those two drugs and alcohol don’t have a direct effect of making psychosis necessarily worse or better, they don’t have direct impact on those symptoms,” said Watts, adding the medication could make people drowsy or lessen anxiety.
“The fact that he had not been taking his antipsychotic medication regularly definitely had an impact on the worsening of his symptoms, the worsening of his psychosis,” Watts said.
“I don’t think what he was telling me about, in terms of his psychotic experiences, would per se be biased because those are not things that would have been presented to him by anybody else,” he said.
“Only he would have memories of those things, only he would be able to recollect those things.”
The forensic psychiatrist repeated that he believes those symptoms were not fabricated.
Watts and another psychiatrist have testified for the defence that Magnotta was psychotic the night of the killing and was incapable of telling right from wrong.
The Crown is arguing the crimes were planned and deliberate.