I’ve known a couple decent guys from the FBI in California and I once asked about the ‘person of interest’ thing and one of them said it could be applied to people who were possibly witnesses, bystanders, suspects, or maybe just people whose presence at or near a scene needed to be explained. Until the FBI had more info it’s a useful term to apply to someone they need to talk to.
Nope. They invented it and it has zero legal meaning. It’s a more charming word for suspect. It is almost exclusively used as weasel word for those they have formed reasonable suspicion about.
Bystanders, and people with a presence are known as witnesses or material witnesses. That term is completely undefined by the courts and DOJ. Your FBI buddies don’t know what they are talking about.
There is not a single situation described by “person of interest” that is not already fully and exclusively covered by existing legal terms.
“witnesses, bystanders, suspects, or maybe just people whose presence at or near a scene needed to be explained.”
IE.. witnesses, potential witnesses, suspects, and potential witnesses.