Did you commit a murder in New York City in the last forty years and never got caught? Might want to be careful where you leave your DNA. See, the Manhattan District Attorney's Office this year started a DNA-based cold case squad and is slowly working through the evidence from at least 95 of the city's roughly 3,000 unsolved murders. When they can find the evidence bags, at least.
Thanks to advances in DNA science genetic testing has become much easier to pull off. Where once it took lots of saliva or blood to make a match scientists now just need a nanogram's worth of cells or body fluids. DNA at the scene of a crime doesn't necessarily solve a case, but it does offer up new avenues for police to explore. Especially since 2006 when the number of convictions eligible for DNA collection was expanded to include some petty larcenies, giving cops a wider net of cons to fish through.
The trick in New York is finding the evidence to search for DNA in the first place. Barry Scheck, the co-director of the Innocence Project (and recent guest star on The Good Wife), tells the News that when the Project asked the city for DNA in 46 cases from 2004-2009 the genetic evidence in 27 cases couldn't be found. So just think about how hard it is to find evidence more than a decade old!