Question about citizen's arrest

I was just reminded of a question I had about citizen’s arrest. I was watching Cops years ago (sorry but I don’t remember the jurisdiction) and the officers had someone in custody in the back of a squad car and instructed the alleged victim (I don’t remember the alleged crime or whether it was a felony either) to inform the suspect that he was under citizen’s arrest. Can anyone guess as to the point of this formality? Sorry to have so little information to go on.

Thanks,
Rob

I’ve seen them do this in California at least, where cops can only make an arrest for certain crimes (maybe only misdemeanors?) if they witness the crime. So if the cops did not see it occur, they get the victim (who obviously witnessed it) to make the arrest.

You are correct if for CA. Atwater has an Appendix of state laws on “warrantless misdemeanor arrests”, some require the crime be committed “in presence” of the officer.

I did not recheck current CA law since Atwater, am assuming it is the same for now.

My state, Ohio, has a mostly “in presence” requirement for misdemeanors with a few exceptions though.

No citizen can arrest for misdmeanors here though.