PFO is also an acronym for persistent felony offender. "Persistent felony offender" is the phrase used, at least within some court systems, to describe a person who falls under what are commonly known as repeat offender or three strikes laws. These laws are used to increase the sentence handed down for a person convicted of a second or third felony. Often, the defendant must also meet other criteria, e.g., the convictions occur within x number of years of each other or the defendant must be at least a certain age, for the PFO statute to come into effect.