Yeah, I think mantraps are illegal.
I had a friendly argument with another over a similar (maybe the same) case. He wondered if I thought the deceased “deserved” what he got. I said I don’t know whether they did or not, only that you take you don’t know what you’re in for if you trespass onto another’s property. And that it’s hardly surprising things turned out the way they did.
If mantraps. are illegal then stop all of the undercover sting operations which essentially bait people.