One from my more distant past, my forensic science days. We definitely weren't police but the police were inevitably our biggest "customer". One way or another* the local station got to know my address, or at least that I lived in their area and my phone number was in the book. Late one Saturday evening I got a somewhat apologetic call. It wasn't anything to do with my work but would I come into the station because they wanted an independent witness.
They'd arrested a drunk. You may have heard the expression "feeling no pain" as a euphemism for being drunk. For this guy it wasn't a euphemism, more like the literal truth; he must have been well anaesthetised. He was head-butting the cell door and shouting. By the time I got there he'd damaged one cell door - two layers of wood interleaved with a steel sheet and had to be put in another cell. They thought he'd broken his nose in the process and he'd bled all over the first cell. He was continuing to hit the cell door. There was no way I could actually go into the cell to see inside but there was a continuous racket coming from it: bang, bang, bang, "I want my solicitor", bang, bang, bang, "I want my MP", bang, bang, bang, "I want my solicitor"... Never heard anything more about it.
* It may have been because the station sergeant was a former senior SOCO. We came across him once off-duty in the local supermarket following the store detective. He suspected she was on a bonus for each case brought to court and was slipping merchandise into unsuspecting victims' shopping bags. He eventually caught her.