tail 'em, nail 'em, and jail 'em
The strategy of following someone who is on probation or parole with the strict, likely prejudicial intent of arresting them immediately when they do anything that would breach the terms of their probation or parole. The sheriff's office has a strict policy of tail 'em, nail 'em, and jail 'em in this county, so if you don't want to go back to prison, then you had best walk the straight and narrow for the entirety of your parole. Studies are increasingly showing that "tail 'em, nail 'em, and jail 'em" policies don't reduce crime, they just keep our prisons overflowing with inmates.
n. the police in general; a police officer. Old nail-em-and-jail-em is going to be knocking at your door any day now. Victor mooned a nailer and almost got nailed.