THE THOUGHT OF THEIR WIFE WITH ANOTHER MAN will spin most guys into an understandably blind rage. But even if you think she’s cheating with another man in his house, if she’s there of her own free will, the law says you don’t get to enter the home by going full battering ram on the front door (and then the dude). That’s the line 31-year-old John Fisher crossed late last month in Scott County, Missouri, when he went looking for his wife—and ended up getting shot dead for the trouble.

When three would-be burglars attempted an ill-advised dynamic entry into a Houston apartment late Wednesday, they probably weren’t expecting to meet the Lone Star ...