In a prelude to the robbery in Kirkland House that ended in Justin Cosby’s death, alleged gunman Jabrai Jordan Copney and his alleged accomplice Blayn Jiggetts are said to have stolen a large quantity of marijuana from two Yale undergraduates in 2008, according to court documents.

Copney allegedly told Jules E. Bolton, a 2009 Yale graduate, that he would pay $14,000 for three pounds of marijuana; instead, Copney robbed Bolton and his friend at gunpoint, taking the marijuana and their IDs, Bolton told investigators.

According to a memorandum filed by the Middlesex District Attorney’s office, Jiggetts said that the incident in New York served as a blueprint for the robbery in Kirkland’s J-entryway on May 18, 2009.

That day, Copney allegedly shot Cosby, a Cambridge Rindge and Latin graduate who did not attend Harvard, during what investigators have called a failed “drug rip.”

Chanequa N. Campbell, a Harvard senior at the time, and Jason Aquino, another alleged accomplice who plans to plead guilty to manslaughter Thursday for his role in the shooting, both told investigators that the robbery of the Yale students served as a model for the plan to rob Cosby.

Prosecutors described this alleged robbery in a memorandum that responds to a motion filed by Brittany J. Smith, who is being charged with misleading a grand jury. The motion filed by Smith asked prosecutors to drop charges against her due to a non-prosecution agreement.

In their memorandum, prosecutors say that the agreement with Smith should be nullified in part because she did not disclose that she was aware of the robbery of the two Yale students. Because of this, prosecutors say, she violated an agreement to cooperate with investigators, a claim that her defense attorney strongly disputes.

ANOTHER DRUG RIP

Bolton told an investigator in Sept. 2009 that he and Yale classmate Alexander T. King met with Copney in Brittany J. Smith’s Lowell House dorm room during the weekend of the Harvard-Yale football game in 2008, according to the memorandum.

Smith was Copney’s girlfriend at the time of the Kirkland shooting and has been charged as an accessory to the murder.

Campbell told investigators that she was friends with King before that 2008 meeting.

Bolton said that in Nov. 2008, Copney told Bolton that he planned to return to New York, where he, Jiggetts, and Aquino are from. According to the document, the two finalized the details of the drug deal and planned to meet at a Starbucks near Grand Central Station in New York City.

The District Attorney’s Office wrote that prior to their New York meeting, Copney told Bolton that he would give him $14,000 for three pounds of marijuana, according to court documents.

Bolton, prosecutors said, told investigators that it was an unusual deal for him because most of his past deals were smaller and were done in his dorm room at Yale with people he knew.

Copney was about 45 minutes late to their meeting, which Bolton told investigators unnerved both him and King.