The general rule is that you can record things that happen in public, especially things that happen on your property. Courts have rules for introducing this type of evidence. You are better off having a lawyer help you. Or, find out the rule in advance.
David A. Mallen offers answers on Avvo for general information only. This offer of free, general answers is not intended to create an attorney-client relationship. If you need specific advice regarding your legal question, you should consult an attorney confidentially. Many experienced California labor and employment attorneys, including David A. Mallen offer no-risk legal consultations to employers and employees at no charge. David A. Mallen is licensed to practice law before all state and federal courts in California, as well as the California Labor Commissioner and the California Unemployment Insurance Appeals Board. Failure to take legal action within the time periods prescribed by law could result in the loss of important legal rights and remedies.