DNA has the power to cut short nightmares -- the horror of an innocent man behind bars for a crime someone else committed, the fear of a murderer walking free and looking to kill again.
In the past 16 years, DNA testing has freed scores of prisoners found to be wrongfully convicted, resolved old mysteries including murders and rapes and transformed the debate over the death penalty. It has shaken the foundations of the criminal justice system itself.
DNA proved pivotal again on Thursday, when an analysis confirmed that Roger Keith Coleman was indeed the man who raped, stabbed and nearly beheaded his sister-in-law, as a jury concluded.
Coleman was executed in 1992, proclaiming his innocence as he went to the electric chair.
The case was closely watched by both death penalty advocates and protesters because no executed convict in the US has ever been exonerated by scientific testing.
Despite the lack of an explosive result in the Coleman case, the power of DNA is unquestioned and is sure to come into play again.
Advocates for reform remain convinced that there are other executions that need to be retested, sure that an innocent person somewhere along the way has been executed -- even as prosecutors and courts have been hesitant to go back and revisit cases that juries and courts have deemed closed.
"There are many more like the Coleman case," said defense attorney Barry Scheck, co-founder of the New York-based Innocence Project, a legal clinic that seeks to exonerathe inmates through DNA testing.
"DNA has shown, whether it's the death penalty or not, there are flaws with eyewitness testimony, false confessions and crime labs. We know many more people have been wrongfully convicted than anyone thought." Scheck said.
It took years of effort to get DNA evidence accepted by the courts, with the first exoneration -- of David Vasquez, convicted of second degree murder in Virginia -- coming in 1989. It began with a trickle, and then became a flood. The 100th exoneration came in late 2001.
"There are all these cases. There's a crescendo of cases, of innocence," Scheck said.
And the impact has hit everyone from police officers to judges.
"It was a world-shattering event," said Geoff Alpert, a criminal justice professor at the University of South Carolina. "It's kind of like computers. That's how my kids think of it. The before and after differences are enormous."
Scheck and others such as Centurion Ministries, a New Jersey organization that investigated Coleman's case and became convinced of his innocence, argue that with DNA tests exonerating 172 wrongfully convicted prisoners over the years, the technology raises bigger questions about the justice system itself.
By proving flaws, DNA raises doubts about other cases in which genetic testing doesn't play a part. DNA only can help in cases where biological evidence ties the victim to the criminal, such as rape cases or murder cases where the criminal's blood or skin -- or maybe even a chewed-up piece of gum -- is left behind.
But DNA evidence cuts both ways -- as in the Coleman case.
Death-penalty supporters say DNA can help strengthen the case for capital punishment by determining with scientific certainty that those convicted are guilty.
Such supporters say they're willing to support ways to curb flaws that lead to wrongful convictions -- from presenting photo lineups of suspects to victims to videotaping police interrogations that can lead to false confessions. But they dismiss allegations that DNA evidence proves the justice system is deeply flawed.