In a landmark case for the state, Aaron Deveau, 18, was found guilty on charges of vehicular homicide, texting while driving, and negligent operation of a motor vehicle.
Prosecutors said Deveau's texting while driving caused a crash that led to the death of 55-year-old Donald Bowley.
The trial got under way last week in Haverhill.
The crash took place February 20, 2011.
Prosecutors said Deveau was texting when his car crossed the center line and hit a vehicle being driven by Bowley, a resident of Danville, New Hampshire.
Bowley's girlfriend, Luz Ramos, was in his car with him and suffered serious injuries.
Haverhill Detective Thomas Howell testified the impact left the two "almost folded into the floorboards."
Bowley died March 10, after he was taken off life support.
"My brother received such head trauma that ... there was no hope for him," Bowley's sister, Donna Burleigh, said in court.
Assistant District Attorney Ashlee Logan argued that Deveau may have erased some of his texts or lied to police after the accident about when he was texting.
Deveau said after the crash in a taped interview with police, which was played in court, "I was tired. I was distracted. When I looked away for one quick second, I came too close to her and I was trying to hit my brakes."
His defense lawyer claimed authorities set out from the beginning to link texting to the crash, a cause-and-effect relationship that he contends is not valid.
Some 38 states ban text messaging for all drivers while 31 prohibit all cell phone use by "novice drivers," according to the Governors Highway Safety Association.
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