Blackmailing the Criminal
Someone who can easily prove another person commited a crime decides to blackmail them instead of reporting them to the authorities.
Alice has witnessed Bob commiting a crime and can prove he did it, but instead of reporting him to the authorities she decides to squeeze some money out of him. In cases where the crime is murder, the blackmailer usually ends up murdered themselves.
- Letter to my Killer
Hello, Unknown Troper. You'll need to get known to lend a hand here.