These are the games that lawyers play. If a hired psychologist/psychiatrist’s opinion is helpful to the lawyer’s case, they may use it. This is the lawyer’s decision (except in cases where the psychiatrist is appointed specifically by the court). If the expert opinion does not support the lawyer’s case, it won’t get used, and the evaluation remains hidden from the court. So the expert testimonies you see in court are most likely going to be favorable for the one who retained the expert. In some cases, a lawyer might hire many experts until he finds one whose opinion supports the case. In my experience, there are always a few fringe go-to witnesses who frequently pop to take some $ and testify something retarded.
I don’t have a strong desire to debate with mental illness deniers on an Internet forum for the same reasons I don’t debate creationists and flat earthers.