The pickup truck driver who caused a chain-reaction crash that killed a motorcyclist on the H-1 freeway last year began serving a six-month jail term Monday for negligent homicide.

The term is a condition of a five-year probation sentence a state judge imposed Monday on 21-year-old David Franco, who pleaded guilty Oct. 1.

Circuit Judge Edward Kubo also suspended Franco’s driving privileges for five years and ordered him to perform 1,000 hours of community service and pay $9,105 to the victim’s widow.

Retired Navy Command Master Chief John David Tyner, 49, died in the March 31, 2011, crash on the freeway in Pearl City.

Police said Franco’s pickup crossed a solid white line on the freeway onramp from Moanalua Road and hit a car that careened across all of the westbound lanes and crashed into the Zipper Lane barrier.

Tyner hit the back of the car and was thrown from his motorcycle. He died at the scene.

Deputy Prosecutor Sheila Nitta told Kubo that Franco lost control of his truck because he was driving too fast at night in the rain in a vehicle that he knew had defective brakes. She said police estimate Franco’s truck was traveling 38 mph on the 25 mph onramp.

Nitta said Franco did not have alcohol in his system, but that a blood test showed a small amount of marijuana. She said Franco told police he had smoked marijuana two days before the crash.

Franco apologized to Tyner’s wife, daughter and mother-in-law, who appeared in court for his sentencing, and said he doesn’t know whether he could bear the loss that they’re experiencing.

Tyner’s wife, Mary, and daughter Nancy Malia did not see the crash. But they told Kubo they have nightmares imagining what Tyner went through when he sustained his fatal injuries. They said the death, to this day, has left them gripped with grief.

In December last year, eight months after the crash, police cited Franco for driving while intoxicated.

Franco pleaded no contest in June and was ordered to pay $662 in fines and fees and undergo a substance abuse assessment.

Nitta said Franco never underwent the substance abuse assessment, lied to court officials about his past drug use and showed up for a meeting with a probation officer seeming drunk or high. She also said Franco failed to complete his probation for a shoplifting conviction in California before moving to Hawaii.

Defense lawyer Steven Nichols told Kubo that Franco’s behavior is that of a young man from a broken home who is struggling to come to terms with Tyner’s death while looking for a job and a place to live.