Kelly McCarron, the teenaged driver behind the wheel during an accident last June that claimed the life of her passenger, 18-year-old Jena Pothier, was sentenced to a year in state prison last Friday by an Edgartown district court judge.

Part of a plea bargain with the Cape and Islands district attorney, the sentencing took place in an emotional courtroom after Ms. McCarron, 18, pleaded guilty to a charge of motor vehicle homicide while operating under the influence of alcohol.

All other criminal charges against her were dropped, including operating a motor vehicle under the influence of alcohol by negligent operation, and motor vehicle homicide by negligent operation.

She was found responsible for four civil infractions: speeding, marked lanes violation, failure to wear a safety belt and improper tire depth.

Judge Gregory Williams agreed to the plea bargain and sentenced Ms. McCarron to two and a half years in the Barnstable house of correction, with one year to be served and the balance suspended. Ms. McCarron will be placed on probation for five years after her release from prison; during that time she must complete 500 hours of community service and remain drug and alcohol free, subject to random testing.

She also agreed to participate in the prosecution of anyone who is charged with providing alcohol to her and Ms. Pothier on June 11, 2009, the day of the fatal accident.

The accident, which shook the Vineyard community, where both girls and their families are well known, took place three days before Ms. McCarron, 17, was slated to graduate from the Martha’s Vineyard Regional High School. Ms. Pothier had just completed her freshman year at Plymouth State University in New Hampshire. The two girls were friends.

They were headed up-Island on the Edgartown-West Tisbury Road in a 2004 Toyota Camry driven by Ms. McCarron, just past the entrance to the Martha’s Vineyard Airport at around 10 p.m., when Ms. McCarron reportedly accelerated to pass a vehicle ahead of her. She swerved back into the westbound lane to avoid an oncoming car, and lost control of the vehicle, hitting a tree. Ms. McCarron was thrown from the car and Ms. Pothier was pinned in the front passenger seat. She died two hours later at the Martha’s Vineyard Hospital. Ms. McCarron was seriously injured and transported to Massachusetts General Hospital in Boston for treatment. She missed her high school graduation ceremony.

Speed and alcohol were both factors in the accident.

Cape and Islands assistant district attorney Laura Marshard said last week that police are still investigating whether someone provided alcohol to the two teenage girls, but she declined further details. “All I can say is the investigation is ongoing, and we are continuing to work with police on this matter,” she said.

A police report following the accident said that on June 11 Ms. Pothier and Ms. McCarron attended a cookout, visited friends and went for Chinese food. In the afternoon the girls parked near a package store in Oak Bluffs, and Ms. Pothier got out of the car to talk with a man who worked at a nearby moped rental shop, according to the report.

The man was later seen giving Ms. Pothier a half-gallon bottle of alcohol with a red label, according to eyewitness accounts cited in the report.

Ms. Marshard told Judge Williams that if the case had gone to trial, the commonwealth would have proven that Ms. McCarron was driving the vehicle, with Ms. Pothier as her passenger, at a speed of 86 miles per hour when she lost control of the vehicle and went off the road.

Her blood alcohol level at the time of the accident was .23, nearly three times the legal limit, Ms. Marshard said.

On Friday, family members and friends of both girls filled the main courtroom in the Edgartown courthouse. Ms. McCarron, a slight figure wearing a white summer blouse, stood behind the bar during the plea and sentencing, and while Vicky Hanjian, a grief counselor, read a wrenching victim statement on behalf of David and Terry Pothier, Jena’s parents. It said in part:

“We had a good life . . . but that life ended on June 11, 2009 . . . The scene plays over in our minds every day as we try to cope with Jena’s death. We wake up each morning, with tears in our eyes, thinking about what happened, questioning again and again: is this true? Did Jena really die? What will we miss today? How will we get through the day? We say good morning to her picture, outlining her profile with our finger, and ask God to get us through another day.

“Jena’s death has been emotionally, physically and financially devastating to us . . . you know a heart really aches with physical pain when it is broken. And ours is broken. It hurts all the time. We wonder if it will ever heal.

“I used to talk to my daughter on the phone all the time, sometimes two or three times a day. But now I’ve lost my daughter’s voice. I cannot hear her anymore. I don’t know what she is thinking . . . We don’t like the silence in our house since Jena has gone.

“Jena will never have her own apartment, a degree, a real job, get married, have a child. Her dad will never give her hand in marriage. We all lost our future the night she died, and ours will never be the same.

“It’s hard never having the chance to say goodbye. The pain is indescribable . . . We all died a lot that night.”

Following the reading of the impact statement, Judge Williams, moved to tears along with the rest of his courtroom, offered his condolences to the Pothier family. “There is nothing this court can do, there is nothing I can personally say that will alleviate your unimaginable suffering. All I can say is that I wish you some measure of peace,” the judge said.

Charles Morano, defense attorney for Ms. McCarron, said his client was sorry.

“Her only hope is that the loss of [Ms. Pothier], along with someone her age going to prison, might help avert this type of tragedy in the future . . . she wants the whole [Pothier] family to know she is very sorry,” Mr. Morano said.

After sentencing, Ms. McCarron was handcuffed and taken into custody.