HEBER, Utah — Prosecutors say DNA testing will be a key part of the evidence they use against a man accused of killing a teenage girl, whose body was found beaten with rocks along the banks of the Provo River more than 20 years ago.

Forty-nine-year-old Joseph Michael Simpson’s trial got underway Thursday with opening statements. He has been charged with aggravated murder in the 1995 death of 17-year-old Krystal Lynn Beslanowitch.

Deputy Wasatch County Attorney McKay King told jurors DNA testing shows Simpson had sex with the teen and that his hands were on a rock used to kill her.

Simpson’s attorney argued that the DNA wasn’t strong enough to show his client killed the girl.

Simpson faces life in prison without parole if convicted.

He pleaded guilty to murder in 1987 and was paroled eight months before Beslanowitch’s death.