A Long Beach man was sentenced Thursday to 18 years to life in prison for the murder of a Lynbrook woman on a Rockville Centre footbridge two years ago.

Authorities have never offered a motive for the murder, but Maxwell Sherman's attorney suggested later that his client, 18 at the time of the killing, might have been under the influence of alcohol that night.

Sherman, now 20, spoke in an almost inaudible tone for just a few seconds before the sentence was imposed by Judge Meryl Berkowitz in Nassau County Court in Mineola for the murder of Lauren Daverin-Gresham, 18.

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"I offer no excuses. I apologize to my family and [for] the pain I caused them," he said.

Sherman pleaded guilty in April to second-degree murder under an agreement that dismisses a sexual abuse charge that would have required him to register as a sex offender when he gets out of prison. He will get credit for the two years he has already served, making him eligible for parole after serving 16 years, officials said.

"He said he was not in his proper frame of mind and it was very obvious from the evidence that came out during the pretrial hearings that alcohol played a large role," defense attorney William Petrillo of Garden City said outside court. He declined to elaborate.

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Before Sherman addressed the judge, Petrillo turned in the courtroom to face the victim's friends and family and spoke directly to them. He said the Sherman family was "distraught over what happened."

"I am truly sorry, and you are in my prayers," Petrillo said.

But the victim's mother, Kathleen Daverin of Lynbrook, said in a victim impact statement that Sherman had "not shown a glimpse of humanity. He has shown absolutely nothing."

Later, outside court, she added: "He's never shown a bit of remorse."

The victim's uncle, Luke McLaughlin of Mount Sinai, told the judge that although the family did not object to the plea agreement, the sentence was "a slap on the wrist."

"You destroyed a lot of lives two years ago," McLaughlin said, looking at Sherman's back. "Your mother and father must hang their heads in shame," he said, adding he "should be put in a cage for life."

Petrillo said the Sherman family, which has homes in Illinois and Long Beach, decided not to attend due to the heavy media presence.

The bloodied body of Daverin-Gresham was found about 10 p.m. on Aug. 22, 2013, on a footbridge spanning eastbound Merrick Road in Rockville Centre, an area neighbors said was a popular drinking spot for teenagers.

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Police said the victim, who had never met her attacker, was sexually abused, beaten and strangled.

Sherman would have faced a maximum of 25 years to life in prison if convicted of the top count of second-degree murder. A conviction for sexual abuse could have added 7 years.Acting Nassau County District Attorney Madeline Singas said in a statement that "Because of the cold-blooded brutality of this crime, it is just that Maxwell Sherman pay a heavy price for tragically and inexplicably cutting Lauren Daverin's life short."

"It is my fervent hope that today's sentence gives Lauren's loved ones a small amount of closure and peace," the statement said.