A Suffolk Superior Court jury convicted all four suspects of murder on Thursday in the 2001 slaying of a homeless woman who lived in the Harvard Square “Pit,” ending a heated trial that saw sometimes conflicting testimony and lasted more than six weeks.

Prosecutors contended that Io Nachtwey was raped, stabbed to death, and then thrown in the Charles River on Nov. 3, 2001 by the defendants to send a message to her friends, who had refused to join the robbery gang allegedly run by the defendants.

After only five hours of deliberation, the jury found Ismael Vasquez, 27, his 23-year-old brother, Luis Vasquez, Harold Parker, 31, and Scott Davenport, 31, guilty of first-degree murder.

Parker and the Vasquez brothers were also convicted of kidnapping Nachtwey, a Hawaii native who had moved to Cambridge several months before her murder. Luis Vasquez was also convicted of rape.

In sentencing on Friday, all four defendants received life in prison without the possibility of parole, the mandatory sentence for first-degree murder in Mass.

In addition, Judge Patrick F. Brady sentenced Parker and the Vasquez brothers to an additional nine to 10 years in prison for the kidnapping charges and Luis Vasquez to a second consecutive life sentence for raping Nachtwey before she was killed. If the murder charges are overturned on appeal, Parker and the Vasquez brothers would still have to serve out their other sentences.

“We are grateful that the jury saw the evidence and held these stone-cold killers accountable for what they did,” said Suffolk District Attorney Spokesman David Procopio. “We are satisfied that three and a half years of work to bring them to justice was fruitful, but we’re also aware that a life of an innocent young woman was lost.”

According to the Associated Press (AP), defense attorneys said they planned to appeal the convictions and criticized the jury for spending only five hours in deliberations.

The AP also reported that a woman had to be escorted out of court for screaming and crying as the verdicts were read on Thursday.

Procopio said that Parker and the Vasquez brothers were the leaders of a gang that had tried to recruit Nachtwey and some of her friends. But, Procopio said, when Nachtwey’s boyfriend, another “Pit kid” named Gene Bamford, and some other recruits refused to carry out orders from the gang leaders, the defendants struck back by raping and killing Nachtwey.

“She was truly an innocent,” Procopio said. “She was a victim who really posed no threat to these men or to anybody. It was just [the defendants’] violent egos. They were going to prove to her friends that they don’t cross them, and they were going to prove that by killing her.”

Assistant District Attorney Patrick Haggan said during the trial that Nachtwey screamed “at the top of her lungs” after Davenport allegedly stabbed her with a 10-inch knife and that Luis Vasquez then repeatedly beat her with nunchucks before they dumped her body into the Charles River, according to the AP.

Two women who were also initially accused in Nachtwey’s murder had earlier pleaded guilty to lesser charges in exchange for testifying against the other defendants. As part of the deal, Lauren Alleyne, 21, will be sentenced to 12 to 15 years in prison, and Ana White, 21—who has already served more than three years for the incident—will be sentenced to 12 years in prison.

Nachtwey’s parents, who still live in Hawaii, did not attend the trial.

Procopio said that the case brought light to the contrast between Harvard and the people that hung around the “Pit,” the area outside the Harvard Square subway station.

“One of the more striking things about this case was the subculture of homeless youths that frequented the ‘Pit,’” he said. “It was just so striking to us that in the shadow of the world’s greatest university and a few blocks from Brattle Street and million-dollar homes that you had this band of runaways and drifters.”

But, he said, locating and getting Nachtwey’s “Pit” friends to testify in the trial played a key role in the prosecution’s arguments.

“We would not have been able to prove this case without them,” Procopio said. “In large part they were society’s misfits, and yet, although it wasn’t easy for them, when the time came they did the right thing and testified for their friend Io.”

Defense attorneys could not be reached for comment over the weekend.

—Staff writer Reed B. Rayman can be reached at rrayman@fas.harvard.edu.