Diddy Will Testify in Criminal Case, Lawyer Says In New TMZ Studios Documentary

Huge news in the Diddy criminal case ... he's chomping at the bit to defend himself in a federal courtroom ... and he will take the witness stand to tell his story.

Diddy's attorney, Marc Agnifilo, appears in a new TMZ Studios documentary -- "The Downfall of Diddy: The Indictment" -- which is dropping soon on Tubi ... and he tells us Diddy can't wait to testify in court.

It's a risky move ... Diddy's going to be able to tell his side of things, but he's also going to be cross-examined ... and obvious topics include the Cassie beating video, the famous "freak off" parties and accusations he blew up a car belonging to one of Cassie's exes.

Agnifilo acknowledges the gamble here, but tells us there's no one better to defend Diddy than Diddy himself.

The lawyer says Diddy's story involves love, hurt and heartbreak.

Our documentary chronicles Diddy's indictment and defense, plus a ton of issues that have not yet surfaced.