Age 15, high school locker room.
It's a horribly damaging thing to go through. Cruel and unusual punishment of the highest order, scarring a person for life and damaging their ability to interact with the human race. The suggestion that this might be a form of punishment, or a 'mere' side effect of incarceration in our 'corrective' prison system is just unacceptable.
(We have a county-wide holding system for persons arrested here. The Sheriff's Office runs 'holding', and has a history of throwing arrested trans women into the men's holding cell. The sheriff's deputy will check on the holding cell every two hours, on the dot, and otherwise ignore it. You really, really do not want to be trans and arrested here. It is extremely dangerous.)