Pretty sure Ted Bundy had a long time girlfriend. Didn't she turn him in?

BTK was married and cub scout leader and president of his church.

The Golden State killer was married.

John Wayne Gacy had a wife for a bit. He was definitely murdering during his marrage. The wife couldn't figure out the stench from the crawlspace.

Canadian serial killer Russel Williams was a colonel in the army and married.

5 out of how many? Ok, maybe op has a point.