Prosecutor Steve Nelson called the attack heinous and violent and asked for the maximum sentence a request that Judge Judith Atherton granted. The victim did not speak at Friday's hearing.
A jury in February convicted Augustine of first-degree felony attempted murder, declining to convict him of a lesser aggravated assault charge pitched by his defense attorneys.
Augustine testified at his two-day trial, telling jurors he fell victim to his "own passion and stupidity."
Augustine said he was overwhelmed with emotion when he learned he had contracted an STD from his girlfriend, Stacy Kennedy. The girl told him she previously had sex with Ennis and thought she had picked up the disease from him, he said.
Augustine said that after screaming out in pain while urinating the day of the assault, he hatched a plan with his friend, Scott Stapley, to go to Ennis' home and "beat him up."
The two then scuffled in a driveway, but Augustine said he had no idea Stapley planned to join the fight and attack Ennis with a four-bladed warrior ax with a spiky ball attached. Augustine then stabbed Ennis out of adrenaline and fear for his own and Stapley's safety, he testified.
Augustine's attorney, Randy Richards, argued Augustine acted under "extreme emotional distress" that came after learning he had an STD. He said while Augustine had told friends he was going "to kill" whoever gave him the STD, Augustine used the phrase as a figure of speech and did not intend it as a death threat.
Prosecutor Steve Nelson argued throughout the trial that Augustine and Stapley, who was sent to prison two years ago on the same charge as Augustine, concocted a plan to ambush Ennis and meant to kill the teen. Nelson described the incident as a "Hollywood slasher flick."
Police have said Stapley and Augustine are members of the Juggalos, fans of the Insane Clown Posse rap group who are classified as a gang by Utah law enforcement.
Nelson said Friday that more charges could be coming in the case. Prosecutors may pursue second-degree felony obstruction of justice charges against Stapley for refusing to testify against his friend at trial.
If Stapley is charged and convicted, he could face additional prison time or receive a longer sentence from the Board of Pardons and Parole during his February 2012 parole hearing.
Kennedy could also be charged after Augustine revealed in court at his trial that she was in the car during the attack and she helped lure Ennis outside with text messages promising to meet up for sex. Augustine testified he lied to police about Kennedy's involvement in order to protect her and Nelson said the woman could be charged as an accomplice in the case.
Nelson said prosecutors haven't yet made a final decision on filing the additional charges.