Legal Question in Landlord & Tenant Law in California

A landlord never should return any money to the tenant until after they have left the rental property as you do not know what damage they will cause. Also, some people will refrain from damaging the unit only because they want the security deposit back. But remember that within 21 days after they have left, you must return the security deposit less any amount necessary for damages not part of ordinary wear and tear or rent not paid and detailed explanation, with estimates if possible, as to any sums withheld.

Another "Microsoft Tech Support" answer from Shers - completely correct but doesn't address the issue at all. A security deposit is security for performance of ALL the terms of the lease. Most commonly that comes down to security for performance of the duty to return the premises at the end of the lease in the condition received, normal wear excepted. But when you have to evict someone, usually for not paying rent, the security deposit absolutely may be applied to anything you evitcted them for that has a monetary value/loss attached to it. So non-payment of rent, or lost tenants due to breach of the duty not to disturb other tenants, or any other thing you have a right to evict for that has a measureable dollar value, you can deduct from the deposit for, or keep the whole thing if that is how the dollars balance out. Just be sure to give the statement of what you kept the deposit for as Mr. Shers mentioned.