In the movie Primal Fear, the prosecution calls Thomas Goodman to to testify and upon Vail's objection, the judge gives Vail the option to decide whether he wants his investigator to testify or not.
Thomas thinks, and then agrees. Thomas goes on to truthfully answer most of the questions except for the question of whether he stole the tape, to which he said that he only borrowed it.
Did that not beat the purpose of delivering the tape to the prosecutor's door anyway?
Did Thomas not incriminate himself for stealing the tape?
If Vail was so confident of Thomas's "borrow" story, why was the tape delivered anyway rather than it being entered into evidence legally?