Taking something that is not yours could lead to criminal charges. Yet, sometimes people lose things, and if you do not pick them up, someone else will.
If you work in a gym, a nightclub, or public transport, you may encounter lost property while on duty. Your employer should have procedures that tell you what to do. However, not all employers have this, and there are no strict rules on what to do with items you find in public areas outside of work.
California theft law makes a specific mention of lost property. It says if you have a way to find out who the owner is and do not try to do so, you could be charged with theft if you keep the item or give it to someone else.
How hard do you need to try and reunite an item of property with its owner?
The law says you must make “reasonable and just efforts” to find the owner of lost property. That leaves room for interpretation. Let's say you find a wallet while walking along Market Street. If it has a business card in, there is little excuse for not contacting the person. If the only thing in it is a few hundred dollar bills, tracing the owner might not be feasible.
However, if you found the same wallet at a school parent's evening, it would be simple to ask the school to send a note to the parents who attended. If you did not and pocketed the money, the parent who lost it might succeed in accusing you of theft.
If you find yourself accused of theft despite your efforts to trace the owner, seeking help to explain the attempts you made will be crucial to defending against the charges.