SSRI's causing mania and/or psychosis is a well-documented phenomenon. Why should insanity caused by legally prescribed drugs be treated any differently than insanity caused by organic brain dysfunction? As far as we know, it's the same neurochemical process, and since the defendant took the drugs with a doctor's prescription (i.e., not with the intention of getting high), it's really no different than if he had a non-drug-induced manic or psychotic episode.