WOBURN, Mass.—Assistant District Attorney Daniel J. Bennett ’85 said today that Jabrai Jordan Copney lured Justin Cosby, the victim of the May 2009 shooting in Kirkland House, into a basement where he was shot during a drug rip gone wrong.

Cosby met his alleged assailants—who posed as Harvard students to gain his trust—in a basement room in Kirkland where he thought that he would sell a large quantity of marijuana to the men. But, according to prosecutors, Copney and his accomplices instead tried to rob Cosby of the drugs.

Prosecutors said Blayn Jiggetts, an alleged accomplice, held the gun at the beginning of the transaction, but Copney took the gun after Cosby refused to hand over the marijuana. The exact details of what happened during the failed robbery is unclear, but prosecutors say that as Jiggetts reached for the marijuana, Copney fired three shots in the small room.

Prosecutors said yesterday during opening statements in Copney’s trial that the alleged gunman fired wildly—one shot lodging in a wall, another in a door, and a third hitting Cosby in the abdomen.

After being struck by the bullet, Cosby fled the entryway and stumbled down Dunster Street, where he fell to the ground, clutching whatever remaining marijuana he had intended to sell.

Bennett also said that Copney had enlisted the help of Jiggetts and Jason Aquino to provide the gun in the planned robbery.

Copney had become familiar with both Lowell and Kirkland House where his girlfriend Brittany Smith and her friend Chanequa Campbell lived, respectively, Bennett said.

On the day of the shooting, Bennett said, Copney, Jiggetts, and Aquino used the ID of Smith, a College senior at the time of the shooting, to open the door to the Kirkland entryway where the murder took place.

Prosecutors have also said that Jiggetts loaded the gun in Smith’s room as she watched.

The trial for Copney, who is charged with the first-degree murder of Cosby, officially began yesterday at the Middlesex Superior Court in Woburn with opening statements from both sides in the case.

Cosby was a Cambridge resident and was said to have sold drugs to Harvard students.

But in the defense’s opening statement, John A. Amabile, Copney’s attorney, said that prosecutors have tried to pin the blame on his client when, in fact, Jiggetts was the man who pulled the trigger.

Amabile contests the prosecution’s assertion that Jiggetts handed the gun to his client and will argue during the trial that there is not sufficient evidence to prove that it was Copney who fired the shots that killed Cosby.

“A homicide in the hallowed halls of Harvard University. Shocking. Somebody’s got to pay,” Amabile said in his opening statement. “The forces have [pinned it] against Jabrai Jordan Copney ... Does it matter that he’s innocent? It should. It does.”

Amabile said that prosecutors had started their investigation with a foregone conclusion—that Copney had pulled the trigger—and proceeded to construct evidence to support that argument.

As part of that strategy, Amabile said, the prosecution has made plea deals with several key players in the case, including Campbell. Amabile said that investigators have dangled carrots in the form of lesser jail time—and in the case of Campbell, a chance to get her degree—in order to secure their cooperation in the case against Copney.

“She’s thinking that if she comes around, maybe these Harvard alumni will get her reinstated,” said Amabile, referring to District Attorney Gerard T. Leone ’85 and Bennett, who both graduated from the College and lived in Kirkland House. Another prosecutor on the case, David M. Solet, is a 2001 graduate of the Law School.

Three witnesses, including a state trooper, a passerby, and a longtime friend of Cosby’s were called to the stand before court went into recess.

Massachusetts State Trooper Kathryn Downey was the first witness to take the stand. Downey was called to the scene of the crime on May 18 and lifted fingerprints from the front and rear right side doors of Cosby’s car.

The prosecution also showed a video that Downey made, providing a visual tour of the art room under J entryway where Cosby was allegedly shot.

Junior Nash, who had known Cosby since the third grade, said on the stand that Cosby had no job, sold marijuana to earn money, and frequently did so from his car.

The jury is scheduled to tour the area of Harvard today where the killing took place.

Prior to the start of the trial, Jiggetts and Aquino pleaded guilty to lesser charges of manslaughter, though they were both originally charged with first-degree murder. Part of Jiggetts’ agreement was to testify at Copney’s trial.

Campbell will be called to the stand once the trial resumes in Woburn.

—Staff writer Xi Yu can be reached at xyu@college.harvard.edu.