Christine Stoneham (Karen Grassle) is the main villainess from "Murder in a Minor Key," episode 3.14 of Murder, She Wrote (airdate February 8, 1987).
Christine Stoneham is the wife of music professor Tyler Stoneham, but she was shown in an argument with her husband, as she had suspected him of cheating on her while he was supposedly away on business. Later that evening, Christine confronted Tyler at his office, resulting in another fight. This time, Christine killed her husband, doing so by stabbing him with a tuning fork.
Mike Prentice, one of Tyler's students (whose music he plagiarized) ended up being accused of the murder when he was found in Tyler's office. His friend, fellow student Chad Singer, questioned Christine at her home, with the villainess claiming that she had phoned Tyler and was at home watching a sitcom on TV. However, after Chad spotted an inconsistency in Christine's story, he decided to reenact everything that happened on the night of Tyler's murder. The result proved that Christine did not call Tyler, and after realizing that she was exposed as the killer, Christine confessed. Christine was later arrested (off-screen) for killing her husband.