For those who started reading in more recent years, back in 2016, I did a series of posts on the old trope, The Butler Did it. I put a bunch of time into researching it, and it turned out that the butler may have done it, but he didn’t do it very often. This series started with my post, The Butler Did It?
You can read the rest on the tag the butler did it. I went through the stories I could find by searching which actually had a butler as the villain, as well as one radio play.