What are some promising developments in criminal investigation technology that have emerged in recent years?

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.