If I get an expungement, can I legally say that I have never been convicted of a crime in a job application?

Yes- if your case was expunged pursuant to 1203.4 of the California Penal Code, you can legally answer that question with a “no”. However, you still have to disclose the conviction if you are applying for a state job or seeking a public license (real estate, medical, law etc).  Thus, your obligation to reveal the conviction on a job application depends on the type of job. With all private job applications, you can legally say no.