Bleg on criminal prosecution of people for transient possession of illegal objects they want to give to the police

In a recent case in Surrey, England, a man found a black bag in his garden one evening. He looked into the bag, and found that it contained a shotgun. He took the shotgun into his home, and the next day he called the police, and brought the shotgun to the police station. He was arrested for unlicensed possession of a firearm, convicted after a jury trial, and now faces a mandatory sentence of at least five years in prison.

I am asking for commenters who can point to similar cases in the U.K., United States, or elsewhere. For example, a student finds a knife on a playground at school; she picks it up and takes it directly to a teacher. She is expelled for possession of a weapon on school property. I’m not looking only for cases involving weapons.

Also fair game for inclusion are other cases in which the person’s possession of the weapon or other item was patently innocent and transitory. For example, a victim is attacked by someone with a gun. The victim snatches the gun away from the attacker. The victim is criminally prosecuted because he has a previous felony conviction, and therefore is not allowed to possess a gun.

For the cases you describe, please supply a cite, a link, or similar information. Thank you!