A Nevada woman who spent more than three decades in prison has been exonerated based on new DNA evidence in the slaying of a 19-year-old nursing student back in 1976.

Prosecutors formally dropped the murder charge against the woman after the judge threw out the conviction against 64-year-old Cathy Woods, according to a Reuters report.

Authorities matched DNA evidence found on a cigarette butt at the scene of the stabbing near the University of Nevada in September with a prisoner in Oregon, clearing Woods.

The judge initially set a date for a retrial in July, but Washoe County District Attorney Chris Hicks opted to drop the case against her in light of the new evidence.

Hicks said in a statement that there was no point to continuing the investigation into the murder now that the evidence had come to light clearing her.

Michelle Mitchell was a nursing student who disappeared after her car broke down near the University of Nevada campus back in 1976. She was later found with stab wounds to her throat and tied up in a garage.

Three years later, Woods said that she had murdered the woman while in the care of a psychiatric ward in Shreveport, La. When Reno authorities visited her, she said the same thing, and a jury convicted her in 1980.

After the Nevada Supreme Court voided the conviction, a second jury found her guilty again in 1985, and was again sentenced to life in prison.

Fast foward to 2010, and her lawyers requested that DNA at the scene be tested, particularly a cigarette that was close to the body. It matched a profile that was connected to two unsolved murders in early 1976 in California, and then last year it was matched to Oregon inmate Rodney Halbower, who had been in prison in Nevada for a different crime and was transferred to Oregon, but not before his DNA was recorded, allowing Woods to be exonerated.