I don’t know the answer to the following, so maybe someone wants to take it a crack at it.
If a person has a mental illness, for example; what about a serial killer or any killer for that matter. Anyone that commits a murder and is convicted of such, no doubt about it, he’s guilty, psychiatrists will sometimes come to court and state under oath that the defendant is “suffering” from any number of mental illnesses, like bi-polar, codependency, etc. It's the defendant’s hope that the jury will take his illness into consideration, if not for the verdict, then maybe the sentence.
My point is that if a psychiatrist states that someone is “suffering” from a mental illness are they actually “suffering” if they don’t know they are “suffering.”