What is a DNA expungement?
In California, anyone convicted of a felony, anyone convicted of a misdemeanor with a prior felony conviction, anyone on probation, parole, or supervision for a felony or with a prior felony conviction, and anyone required to register under California Penal Code sections 290 (sex offense) or 457.1 (arson), is required to give a DNA sample. Previously, DNA samples were also collected from anyone who was even arrested for certain felonies—but the California courts are still working out whether or not it is constitutional to take DNA samples from someone who has only been arrested and not convicted. These DNA samples are kept in a state and national database, and then used by law enforcement agencies to identify suspects involved in other crimes.
Usually when a sample of your DNA is taken, it will be kept in the California state database (CAL-DNA program), and the information may be shared with the national database (kept by the FBI), which can be searched by law enforcement agencies around the country.
If you had to give a DNA sample because of your arrest or conviction, you may want to consider getting your DNA expunged from the state and/or national databases. As long as your DNA remains in the database, law enforcement agencies can use your DNA to try to connect you (even incorrectly) to other crimes. Getting your DNA expunged from a database means that your DNA sample will be destroyed and all related information (your DNA profile) will be completely removed from that database.