Okay, the witness cannot testify to his opinion of the defendant's truthfulness. But then why is it okay for the prosecution to ask if the comments made by the defendant showed "spite or ill will" toward the victim? Isn't that also asking for an opinion of the state of mind of the accused? How is the witness qualified to testify to one but not the other?
It's not. But O'Mara didn't object because he didn't mind the answers.
It's okay to ask about defendant's tone, demeanor and other indicia. The issue comes when assigning ultimate conclusion. E.g., "(I think) He had or showed ill will" or "(I think) He was lying" or "(I think) He was telling the truth." Those issues are for the jury.