Yes, it is expungable. You should know that an expungement in CA doesn't clear the record, but rather dismisses the case. In any event, it's a good thing to get done. Use AVVO to find an attorney. Many of us offer free consultations. Best of luck.
There is no such thing as a true expungement in California. When people use the term, they are usually referring to a dismissal under Penal Code §1203.4, which has some benefits but does not seal the record.
If your cousin went to prison for the offense, he is not eligible for a 1203.4 dismissal. Even if he's eligible, it would have no effect on his requirement to register as a sex offender. The offense that requires registration is probably a bigger deal than the failure to register.
This is NOT legal advice. It is a general discussion of legal principles by a California lawyer, and does not create an attorney/client relationship. You should always consult PRIVATELY with an attorney.
The PC290 offense itself is eligible for PC1203.4 "relief" but the underlying conviction that requires registration, likely, is not. I don't see where this will help in any fashion.
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