” If he was actually hallucinating it was due to some other substance or mental defect.”
In the ‘70’s I had a business partner who later developed schizophrenia, which was a family problem. He had one toke on a joint that probably six other people shared with no ill effect. He was in bed with hallucinations for three days. I realize now that there were plenty of other predictive indicators if I had recognized them. That was probably the first visible symptom that he had a larger mental issue.
Just out of curiosity, how was he as a business partner before he, uh, blew up? Was he sociopathic? charming? Distracted? Honest/self-serving? I've had some less-than-desirable, but not-hospitalized partners in the past, myself.