"We have chosen at this time to dismiss the case, and it still continues to be an open homicide," Gill said Tuesday.
Younge's attorney, Michael Misner, said Tuesday that he felt that the slaying was likely connected to Younge because he had been in the area at the time and was facing charges of beating, robbing and raping another University of Utah student a few years earlier.
"Whatever Donald Younge has done in other times of his life, he just didn't commit this crime," Misner said of the homicide. "They just had the wrong guy."
Just after midnight on Aug. 3, 1999, a man broke into a Salt Lake City apartment and held three women at knifepoint in one of the bedrooms. After taking the women's wallets, the man stabbed Erin Warn, who was 19 at the time, and Quinton.
Warn was shown more than 100 photographs of possible suspects, but never positively identified her attacker, she testified in court, but said she would know the man if she saw him. When she took the stand at a 2009 preliminary hearing, she looked at Younge in court and said she was "100 percent" certain he was her attacker.
The other survivor, Lynn Drebes, 37 at the time of the attack, also testified it was Younge who attacked them in her apartment.
But Misner argued in court in July 2011 that the testimony of the two eyewitnesses should be excluded from the trial, claiming their identifications. Misner noted that the two women never identified Younge until he was in court.
At that same 2009 preliminary hearing, prosecutors presented no fingerprints or DNA evidence linking Younge to Quinton's death.
Misner said Tuesday that there may have been DNA evidence or fingerprints taken from the scene, but they didn't match Younge. Gill declined to comment about specific evidence.
Misner said he has not talked to Younge since the charges were dropped, but said Younge knew that a dismissal was likely coming.
"Obviously, he's relieved that he doesn't have to worry about potentially being executed for something he didn't do," Misner said.
Younge was sentenced in 2010 to spend 31 years to life in prison for the 1996 sexual assault of the other U of U student. Younge, of Illinois, was charged in the cold-case rape because of a DNA match.