HILO, Hawai'i — Parole officials have ordered a Big Island man who caused the death of two women during a high-speed chase in Kona in 2006 to serve all 20 years of his prison term without parole.

Vernon E. Costa, 43, was convicted of two counts of manslaughter in the deaths of Pua Lei Santa-Isabel, 26, and Casey Ann Swain, 35.

Police alleged Costa used a pickup truck to run the women's car off the road on July 16, 2006, because it was also carrying his former girlfriend, Janelle Nardin, who survived the crash.

Costa pleaded guilty to two counts of manslaughter under an agreement that required prosecutors to drop more serious charges of first-degree murder, two counts of second-degree murder and attempted second-degree murder. If convicted on those original charges, Costa would have faced life in prison.

Costa's lawyer argued that the crash was an accident, and Costa never intended to kill the women. To convict Costa of murder, the state would have to prove Costa deliberately killed the women.

As another condition of the plea, prosecutors agreed to not seek consecutive sentencing in the case. That means Costa will serve his sentences for the less serious offenses of leaving the scene of an accident, assault, criminal property damage and possession of drug paraphernalia at the same time as he serves his prison terms for manslaughter.

Max Otani, parole administrator, said Costa will be able to apply for a reduction in the 20-year minimum term set by the Hawaii Paroling Authority in his case once Costa serves one-third of the 20-year sentence. However, Otani said the authority rarely approves significant reductions in minimum terms.