Legal Question in Real Estate Law in California

You are required to disclose anything that is (a) known to you, and (b) might affect the purchase decision of a reasonable, typical buyer.

Bryan's response is accurate. However there is no specific statute covering the issues you have described. There is, for example, a requirement that you disclose a recent death on the premises. I do not think the issues you describe, without more, would require disclosure. If, however, the prior conduct may result in gang members shooting at the home, or if the criminal acts involved illegal drug production which may impact the homes livability, or may result in addicts knocking on the door, these are elements that would require disclosure.

So his answer is correct. Consider what would impact your decision to buy, assuming you are a reasonable buyer. Keep in mind that what you fully disclose is the Buyers problem. What you do not disclose may continue to be your problem, For this reason, you should err in favor of disclosure.