LISBON — Consecutive life prison sentences imposed on a man convicted in a brutal machete attack on a father and 10-year-old daughter in Pittston were excessive, surpassing penalties imposed for attacks in which the victims were killed, the defendant’s lawyer told the state supreme court today.

The lawyer for Daniel Fortune asked the Maine Supreme Judicial Court to overturn the sentence, and argued that evidence was insufficient to uphold convictions.

“That sentence is erroneous because it’s unconstitutionally disproportionate to the crime,” defense lawyer Arnold Clark told the panel in a session held at Lisbon High School.

Kennebec County Deputy District Attorney Alan Kelley said the extreme cruelty justified the harsh sentence in a case that was “straight out of horror movies, the slasher movies.”

Fortune was convicted of attacking William Guerrette Jr. and the girl during a late-night home invasion that left both near death and permanently injured. Nicole Guerrette lost part of her skull due to blows to her head and spent six weeks in the hospital.

Guerrette’s wife jumped out a second-story window to save herself from the attack, a teenage son fled through a basement door and another daughter hid under her bed. One son wasn’t home at the time.

Fortune was convicted of aggravated attempted murder, attempted murder, elevated aggravated assault, robbery, burglary and violating bail conditions. His roommate and foster brother, Leo Hylton, is serving a 50-year sentence for his role in the attacks in May 2008.

The life prison sentence imposed by Justice Michaela Murphy is believed to be the first time in Maine in which the state’s harshest punishment was imposed for a crime in which the victims survived. Judges must abide by strict guidelines set by the state supreme court to impose a life sentence.

Today, Clark pointed out cases in which lesser sentences were imposed for murder, including a 40-year sentence handed down to Nathaneal Nightingale two weeks ago for murder and manslaughter in the shooting deaths of a husband and wife at their home in Webster Plantation.

Clark said the imposition of life prison sentences should be reserved for murders. “We’re blurring the line between murder and attempted murder,” he said.

Justices challenged him repeatedly on what constitutes “extreme cruelty,” one of the conditions that must be met for the imposition of a life sentence.

Chief Justice Leigh Saufley noted that both victims nearly died from their injuries and blood loss, and that both were irreparably harmed. Justice Donald Alexander asked Clarke what would be the base prison sentence for “cutting away part of a 10-year-old’s brain.”

Kelley said he couldn’t fathom a crueler crime, with the father being attacked and slashed and then watching as his 10-year-old daughter was attacked.

“From my perspective,” it’s the cruelest case I’ve been involved in prosecuting from the past 32 years,” he said afterward. “It’s the most horrific crime I’ve dealt with.”

Prosecutors contend Fortune enlisted Hylton in an attempt to silence family members who might act as witnesses against Fortune in the theft of a safe containing money and other valuables from the Guerrette home.

Fortune contended he went to the Guerrette home but that Hylton did all of the slashing. He also contended the evidence failed to show both premeditation and extreme cruelty, elements necessary to support the aggravated attempted murder conviction. He also contended the judge erred in jury instructions and in the consecutive life sentences.

Kelley maintained during Fortune’s trial that Fortune planned the attacks, gave Hylton directions to the Guerrette home and participated in the late-night invasion and attacks. Fortune had been friends with Guerrette’s son and visited the family’s house many times.

A supreme court decision on Fortune’s appeal is likely months away.

The court heard the case in Lisbon as part of its series of sessions in schools across the state. Earlier in the week, the court heard arguments at Deering High School in Portland and at Pownalborough Courthouse in Dresden, where one of the nation’s founding fathers, John Adams, argued cases in 1765.

Saufley said the court has held sessions in 15 to 18 schools in the past six years, giving students a civics lesson and getting the justices out into communities. “It is universally a good experience. Students get to see how the law comes to life,” she said.