Diddy, Prosecutors Square Off Over His Mental 'Capacity' to Commit Crimes

Part of Diddy's defense involves his mental capacity to commit the crimes while he was, essentially, wasted -- he even has a doctor lined up to testify -- but the feds think it's a totally irrelevant point.

Prosecutors filed their opposition to this line of testimony, and in the docs they say Diddy wants to have the doctor -- who's a Columbia professor -- testify he had a "mental condition bearing on the issue of guilt."

So, what does that mean exactly?

Well, the detail of his alleged condition is redacted throughout the documents ... but, there are some clues, including a bit about Diddy's alleged drinking and drugging.

According to the docs, obtained by TMZ, prosecutors say legal precedent requires the defense to give proper notice before offering any "evidence of the effects of drugs and alcohol on a defendant's memory or cognitive function."

One other clue is prosecutors describing the doctor's potential testimony as evidence of the "defendant's inability to control [his] behavior."

What's interesting is the federal indictment accuses Diddy of drugging his victims into compliance during the "freak offs" -- but now it's a question of whether Diddy himself was in a haze during the alleged crimes.

Even if he was, prosecutors say the doctor's opinion on whether Diddy was "lucid" is irrelevant. In the docs, they point out the doctor's never personally examined Diddy, and his testimony would be based on his experience with other people.

Prosecutors also want to block testimony of a forensic video expert regarding the Cassie hotel beating video ... which the judge ruled will be admitted as evidence.