Woburn, Mass. (AP) - A New York City man was convicted Friday of fatally shooting a drug dealer inside a Harvard dormitory during a robbery.

A jury of three men and nine women found Jabrai Jordan Copney, 22, guilty of first-degree murder in the 2009 shooting of Justin Cosby, 21, of Cambridge.

Copney was not a Harvard student, but was dating a woman who attended the Ivy League school. Cosby was a drug dealer who lived a few blocks from the Harvard campus, authorities said.

Prosecutors said Copney pretended to be a Harvard student who wanted to buy drugs from Cosby. On the day of the robbery, Copney and two other New York City men - Blayn Jiggetts and Jason Aquino - lured Cosby to the basement of the dorm.

Jiggetts testified that he pulled out a 9mm semiautomatic handgun supplied by Aquino and demanded the marijuana from Cosby. Jiggetts said that after Cosby refused to hand it over, Copney took the gun. Jiggetts said he heard three gunshots, then saw Cosby running. He said he thought the shots had missed Cosby, but said Copney told him he had shot him.

Cosby ran outside clutching his stomach and collapsed. He died the following day.

Copney's lawyer told the jury Jiggetts and Aquino are "liars" who put the blame on Copney so they could cut deals with prosecutors and avoid long prison sentences.

Copney is a songwriter whose compositions have been recorded by various artists, including R&B group New Edition, according to his former lawyer.

At the time of the shooting, he was dating a Harvard student, Brittany Smith. She is accused of giving the men her Harvard electronic keycard to enter the building where the shooting occurred. She has pleaded not guilty to hiding the gun used in the shooting and to helping the three men elude authorities and escape to New York after the shooting.

Chanequa Campbell, a friend of Smith's who was also a Harvard student, also testified against Copney under a cooperation agreement with prosecutors, saying he told her he planned to steal drugs from Cosby. Campbell, who was not charged in connection with the shooting, acknowledged during her testimony that she sold marijuana and cocaine while she was attending Harvard. After the shooting, both Campbell and Smith were suspended from Harvard and not allowed to graduate.

The mandatory sentence for a first-degree murder conviction is life without parole.