KEALAKEKUA, Hawai'i — A Big Island man who caused the death of two women during a high-speed chase in Kona last year pleaded guilty to man-slaughter yesterday and was sentenced to up to 20 years in prison.

The guilty pleas to two counts of manslaughter by Vernon E. Costa, 42, were part of 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.

Conviction on any of those original charges would have required that Costa receive a sentence of life in prison.

Pua Lei Santa-Isabel, 26, and Casey Ann Swain, 35, were killed July 16, 2006 when the car they were in ran off a Big Island highway in Kona as it was being chased by Costa.

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

However, Costa defense lawyer Robert Kim said the crash was an accident, and that Costa never intended to kill the women. To convict Costa of murder, the state would have to prove Costa deliberately killed the women.

Nardin testified at a preliminary hearing that although the truck driven by Costa twice struck the Honda Accord the women were in, those impacts did not cause driver Santa-Isabel to lose control of the car, Kim said.

Kim also said an accident reconstruction showed Costa had run off the road while trying to overtake the women during the chase, and was trying to return to the highway when his maneuver caused the smaller vehicle to lose control, causing the deaths of Swain and Santa-Isabel.

After the crash Costa also flagged down another car and took Nardin to a hospital, Kim said, which demonstrated Costa never intended to kill Nardin.

"If you were going to try to kill somebody, you wouldn't take them to the hospital," Kim said.

Costa also pleaded guilty to two counts of leaving the scene of an accident involving death or serious bodily injury; one count of second-degree assault for the injuries suffered by Nardin in the crash; one count of first-degree criminal property damage; one count of possession of drug paraphernalia; and one count of driving without a license.

As a condition of the plea, prosecutors agreed not to seek consecutive sentencing in the case, which means Costa will be able to serve his sentences for the less serious offenses at the same time as he serves his prison terms for manslaughter. Prosecutors also agreed not to seek extended sentences in the case.

Kim made a statement on Costa's behalf before sentencing in which Costa indicated he wanted to take responsibility for the crash, and wanted to offer some closure to the families of the women who were killed. He also expressed his "sadness and regret for the loss of life."

Costa was close to the Swain family, and Casey Ann Swain's brother saved Costa's life years ago when Costa was injured by a saw and suffered a severed artery in his leg, Kim said. Swain's brother controlled the bleeding and took Costa to a hospital, Kim said.

"For that Mr. Costa was forever grateful, and I think that goes to the intention part, knowing the Swain family, and I think Mr. Costa wanted to express to the Swain family, and the family of Pua Santa-Isabel, his deep regret," Kim said after the hearing.

Deputy Prosecutor Kimberly Taniyama said Nardin and the families of the slain women approved of the plea agreement.

Taniyama told Kona Circuit Judge Elizabeth Strance, "The deaths of Ms. Isabel and Ms. Swain were tragic, and their last few moments of life were filled with terror" because of Costa's actions.

Before sentencing Strance told Costa that "my hope for you is that while you are in prison, in addition to reflecting on what you did, you will be able to make some significant changes in your life" to prepare for life after he is released.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.