To me, this is like one of those classic English murder mysteries, where 37 people have really good motives to want Victor Victim dead.
Generally, the first chapter or so points to a lot of good reasons why it was probably the butler.
You have to read all the way to the end.
It’s never the butler.
The man was suicidal. If you wanted him dead, all you would have to do is pay off the folks at the prison to stand aside and let him kill himself.