In most states, you are required by law to provide a DNA sample upon a conviction of a felony. In most states, Grand Theft is a felony, which would require you to provide a DNA Sample. Regardless, the police are able to obtain a search warrant to have the DNA sample provided in an effort to link to you to other possible crimes if need be. This is normally done when a person has refused to be fingerprinted or refused to provide DNA upon their initial arrest.