PCR stands Polymerase Chain Reaction. It amplifies the quantity of DNA material for testing. IIRC, testing for STRs, i.e. short tandem repeats, and RFLP, i.e. restriction fragment length polymorphism, only test selected portions of DNA samples. With NY wanting to include those convicted of misdemeanors, this stuff could use a fresh examination.
Note to serial rapists. Be sure you pay some dumb college kid (duke lacrosse players come to mind) for semen or blood (to be used in medical research) and after you are done raping, plant the stuff all over the victim.