I very much doubt that the letter from Kohl's says "Pay or we'll prosecute."
I doubt it too - and even if it did, that wouldn't rise to the legal definition of "extortion" in my state. Extortion generally doesn't cover pressing legitimate charges for a crime actually committed in which the individual who might be accused of extortion is the victim.
I'm recalling a case from a couple of years ago, in which a couple of teenagers were accused of shoplifting. They denied shoplifting but were both issued civil demands. One girl paid, the other did not. The store threatened the girl who did not pay with prosecution and, when she continued to refuse to pay, filed charges against only that girl. After the charge was resolved in the girl's favor, the store was nailed to the wall in a civil lawsuit.
Yeah, but you said the charge was resolved in her favor. I'd bet that played a BIG role in her winning the civil suit.
Sure, in that case, but it didn't matter that the person making the threat actually thought the girl was a thief. I'm also aware of a settled case in which a store, having summoned the police to a shoplifting incident allegedly involving three teenagers, issued civil demands to two girls who weren't found by the police to be involved in the incident and ended up paying them money -- bad practices can create liability even in the absence of a threat. The point is, when stores do stupid things -- like threatening criminal charges if a civil demand isn't paid -- they not only risk messing up the prosecution, they risk liability. Stores should have policies that prevent that sort of screw-up, even if the person making the threat thinks that the subject of the civil demand actually stole.