There are semen tests out there, and some of them work, some of them don't. The light will even read subcutaneous bruising on corpses - this is serious stuff.
If your husband calls you and says he's going to be an hour late, comes home at 330 in the morning saying his car broke down and his pants aren't dirty, you might want to test him.
There's a lot of people accused of cheating who are not, and this kit can prove that. However, there's a flip side to that coin.
We had a guy who bought a BMW for his wife on a Tuesday. She went out on Friday night, came back at 3 a.m., and acted funny all weekend. He took the car back to BMW and had the seat taken apart and sent to us for testing - and he caught her.