Under Penal Code 851.8, you can seal and destroy arrest records that occurred within the last two years, and occasionally longer, if you can prove that there was no probable cause to believe that you were guilty of a crime. If you can't prove that, then the arrest was legitimate and it will stay on your record forever. You do not have to answer the question, "Have you ever been arrested?" and it is not a typical question that police ask, as they have access to your arrest record, simply by calling your name into dispatch.
I differ with my colleague on the standard to be applied for sealing records of arrests under PC 851.8. It's not whether probable cause existed at the time of arrest but whether any reasonable person looking at the facts in your case would decide that no reasonable exists today which would justify the arrest
If your charges were dismissed in each case you have a shot at a declaration of factual innocence.