Thread: Title of old black and white movie?

Watched this movie a long time ago, can't remember the title.

Middle aged guy befriends an old wealthy widow by helping her choose a fashionable hat in a store. He convinces her to leave him money in her will, then she's murdered, so he becomes the prime suspect and is taken to trial. his (seemingly cold) wife (Christine?) gives testimony against him, and she seems to hate him, so even though she's implying that he COULD be the killer, the jury doesn't trust her as a witness because they suspect she's just trying to put him away. later he's found not guilty, and it turns out Christine's entire testimony was all an act to fool the jury into reasonable doubt, and that she doesn't hate her husband at all. but when his mistress emerges, Christine goes crazy and shoots/stabs her husband right there in the empty courtroom.

Does this ring a bell to anyone?? Thanks in advance!

Witness for the Prosecution

Made in 1957 starring Tyrone Power and Marlene Dietrich