In a novel version of "Perry Mason," the fictitious (mostly TV) lawyer called the actual perpetrator of the crime to the stand, as a direct witness because she had declined to testify for the prosecution (against Mason's client). Mason won the case with three questions:
Mason: Are you Martha Lavinia?
Mason: Is this your signature on this letter?
Mason: Please read the letter to the court.
It incriminated her.
I understand that this tactic is highly unusual, to say the least. Perhaps it is because a lawyer can't impeach his own witness or ask leading questions, whereas he can do so on "cross."
On the other hand, if a lawyer couldn't get a key (hostile) witness on the stand, except in the "worst" way, why wouldn't he do so?