VERNAL — An oil field worker who fell asleep at the wheel in May and crashed a company truck, killing a co-worker, has pleaded guilty to negligent homicide.

Joseph W. Serfoss, 36, entered his guilty plea Wednesday in 8th District Court.

Under an agreement with prosecutors, the negligent homicide charge will be held in abeyance for one year, meaning the charge will be dismissed if Serfoss does not violate any other laws during the next 12 months.

Serfoss and two co-workers were returning from working in the oil fields of southern Uintah County on May 30, when Serfoss fell asleep, according to the Utah Highway Patrol. The truck went off the road and rolled, killing 23-year-old Heath Mounga. Troopers said Mounga wasn't wearing a seat belt.

Serfoss and his other passenger, 30-year-old Stephen Torres, escaped the crash with minor injuries.

Following Wednesday's hearing, Serfoss paid a $600 plea-in-abeyance fee. He is scheduled to return to court in September 2008 for a review hearing.