Well how the police get your DNA is the process pretty much you get registered into the system when you registered into the system they swab your mouth if not when ur in the police station you will have to do it because it is in the process of signing up for parole or probation they want to get you fingerprinted in the system so what happens is when you commit a crime or a crime has been committed if dna is found they will take it from the scene and hold it until ecentually the person gets finger printed andlegal ttake the DNA ifhe gets trouble or something you want to go that I'm lucky winner up enough for first time in G?d?on equal to the system isn't matching that when the probable computer like and that's how to get you
They don't find you using DNA, they use DNA to confirm that you are the person who left the DNA at the crime scene once they catch you using other means. It's like fingerprints. Unless you have been convicted of a crime and your DNA is on file, they don't know yours.
They can only do that if your DNA is already in the system. If youve ever been imprisoned for a crime or been in the military or if your parents registered your DNA whaen you were younger as many do now then They can run your DNA code thru the computer system until a match is found. If no match is found in an investigation they hold the DNA and run it periodically against new arrests or when a new suspect turns up.