What episode am I thinking of?

A woman commits suicide, but leaves purposely leaves "evidence" behind pointing to and framing her husband for it. I don't remember the details, or why she committed suicide, but there was a pillow found in another room in the house with a bullet shot through it. The husband was initially a suspect for this, but they were able to surmise that he didn't do it, and wouldn't have left such a key and damming piece of evidence around in plain sight, knowing that it's routine that they would search the house. They theorize that she took her life for some reason (again, I don't remember exactly why. The husband did something to her that drove her to it), and staged it to look like a murder, to frame her husband in an ultimate revenge from beyond the grave sort of thing.