Lawyers for both sides outlined their arguments yesterday as they gave their opening statements on the first day of the trial concerning the 2001 murder of a homeless woman who lived in the Harvard Square “Pit.”

Prosecutors contend that 22-year-old Io Nachtwey was raped, stabbed to death and then thrown in the Charles River to send a message to her friends, who had refused to join the robbery gang allegedly run by the defendants.

But lawyers for the four defendants—Scott Davenport, 31, Harold Parker, 31, Luis Vasquez, 22, and his brother Ismael, 27—claim that all the defendants were either innocent bystanders or had left the scene before Nachtwey’s murder.

According to the Associated Press (AP), Michael Doolin, Luis Vasquez’ attorney, said that on Nov. 3, 2001—the night of the murder—his client was “in the wrong place at the wrong time.”

“Luis Vasquez has done nothing wrong,” he told the AP.

And Elliot Weinstein, attorney for Ismael Vasquez, told jurors that there was no gang, and that his client was no longer at the scene at the time of the murder, according to the AP.

“He was not present when the killing acts occurred,” Weinstein told the jurors. “He had walked away and was not there.”

But Assistant District Attorney Patrick Haggan said that the defendants had been recruiting homeless youth into a robbery ring.

“On every single one of those four defendants is Io Nachtwey’s blood,” he said, according to the AP. “They were all part of a team. They all had a purpose. They all had a role.”

Nachtwey’s body was found the day after her murder in the Charles River.

According to friends, Nachtwey was a native of Hawaii who had moved to Cambridge several months before she was killed. She was homeless, and, along with some of the defendants, was a regular at “The Pit” near the Harvard Square T-station.

Haggan said 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, according to the AP.

Two women, who where also initially accused in Nachtwey’s murder, had earlier pleaded guilty to lesser charges in exchange for testifying against the other defendants. Lauren Alleyne, 21, and Ana White, 21, will be sentenced after the trial.

The jury is scheduled to visit the site of the murder today.

—Material from the Associated Press was used in the reporting of this story.

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