He said that he had found them hanging out with his girlfriend and killed them.
Jarrod Baum (45) faces life imprisonment after a jury found him guilty after a month-long trial.
Riley Powell (18) and Brelynne Otteson (17), disappeared just days after Christmas. Their bodies, bound and stabbed, were discovered months later in Utah's West Desert 100 feet (30 m) below an abandoned mine shaft.
Prosecutors claimed that they were killed after they met Morgan Lewis, a friend, at Morgan's Eureka home, which was once a silver mining town. Baum, her boyfriend, was also there and returned home. He became angry at Lewis for not allowing him to have male friends, while Powell was her previous boyfriend.
Lewis claimed that her boyfriend had tied Otteson to Powell, taped their mouths, and then thrown them in Powell's Jeep. He drove them along with Henderson to an abandoned mine near town.
He beat Powell and then stabbed him before cutting Ottenson’s throat. Then he tossed them down.
Fox13 reported that Ryan McBride, a prosecutor, retaliated against Riley & Morgan and made Morgan watch to see what happened.
Friends and family of the couple searched for Lewis for months before he was stopped by police on March 25, in a unrelated traffic stop. She finally agreed to cooperate with police.
The prosecution relied heavily on her testimony, which was challenged by the defense. Dallas Young stated that there was no DNA evidence linking the murders to Baum.
According to KSL, he stated that "you cannot believe (Lewis) and you cannot be persuaded beyond a reasonable doubt."
Prosecutors countered by claiming that Lewis and Baum had burned and bleached significant evidence, thus obliterating DNA.
The death penalty was originally proposed by the prosecution, but the Utah County Attorney David Leavitt rescinded it after vowing to stop seeking capital punishment.
