I would have to highlight the recent advances in DNA technology as one of the more important crime fighting advances in the last 20 years. It has gotten so much more reliable that dozens of people who were wrongly convicted have been released from prison with compensation, while the maintenance of a prisoner DNA database has helped to capture many criminals who had otherwise gotten away clean. Rapes and murders long since considered cold cases have been solved even decades afterwards. This is better for society and the institution of law as a whole. It gives us more confidence in our verdicts and our courts, and offers better protection from crime. Add to that the knowledge that DNA is so much more accurate probably serves as a deterrent to some criminals, and reduces crime in that way as well.
Combine DNA technology with computerized record keeping and the way in which the states share information and combine their law enforcement efforts, and we have a more effective system for stopping crime.