In NYC in 1970 we had a 0.7% rate of violent crime to the population, that rose to 1.2% in 1990 and 1991 and has since dropped to a low of 0.4%
That is a drop of 67% in 30 years.
Since DNA first was used in 1986 to convict a person of a crime, and the first conviction with DNA was 1987, challenges were made and laws passed in 1989, new techniques for commercially available DNA tests arrive in 1992.
The facts are in the history books, the question that is relevant is how much did DNA (and other forensic techniques) play a role in making sure guilty people are convicted and innocent people are not, and how relevant is that in reducing the crime rate.
We know that repeat offenders in violent crimes are down, significantly. Is this because we are catching and convicting the guilty party and taking them off the streets?