A former high school classmate of accused Boston Marathon bomber Dzhokhar Tsarnaev pleaded guilty Friday to charges that he once possessed a Ruger pistol that his lawyer said has been linked to the fatal shooting of an MIT police officer, allegedly by Tsarnaev and his brother.
As part of a deal with federal prosecutors — the details of which were kept under seal by a judge — Stephen Silva, 21, pleaded guilty to an eight-count indictment of drug and gun charges. Prosecutors did not say whether Silva would testify against Tsarnaev, or what type of sentence reduction Silva might receive in exchange for any cooperation.
All but one of the charges Silva faced stemmed from heroin sales he made in Medford last summer to an undercover agent. The eighth charge, however, is the one that makes the Cambridge Rindge and Latin School graduate a potential key witness linking Tsarnaev to the shooting of MIT police officer Sean Collier.
Prosecutors have alleged that a few days after the Marathon bombing last year, Tsarnaev and older brother Tamerlan murdered Collier “by shooting him in the head at close range with a Ruger P95 9mm semiautomatic handgun, and attempted to steal his service weapon.”
Investigators found a 9mm Ruger P95 after a shootout in Watertown between the Tsarnaevs and police, and identified it as the weapon used to kill Collier.
On Friday, US District Court Judge Mark Wolf asked Silva about the government’s accusation that he had possessed a Ruger P95 9mm pistol, with an obscured serial number, in February 2013 — roughly two months before the bombing.
“Did you commit this crime?” Wolf asked Silva.
“Yes I did, your honor,” replied Silva, who used to work as a lifeguard at Harvard’s main swimming pool with Tsarnaev.
The court proceedings did not provide any details linking Silva to the Ruger handgun; however, his lawyer, Jonathan Shapiro, has previously told the Globe that federal agents informed him that his client’s gun charge is related to the Collier shooting.
Later, prosecutor Peter Levitt provided some information about the evidence that Silva would have faced if he had gone trial, including extensive phone, text, and video evidence of his drug transactions with an undercover agent and a cooperating witness.
On the gun charge, Levitt said the government has evidence that, during conversations related to the heroin sales, Silva said that in February 2013 he was in possession of a specific model of a Ruger with an obliterated serial number, and that he later “transferred” the gun to “another individual.”
The government also alleged that Silva illegally obtained the gun from across state lines.
The prosecutor did not name the individual who received the gun, or say why Silva transferred the gun to that person.
After the hearing ended Friday, Silva’s attorney said he is not at liberty to disclose the terms of the plea agreement, other than to say both sides agreed to keep it sealed.
The most serious charge in Silva’s guilty plea is conspiracy to distribute heroin, which carries a minimum 5-year prison sentence and maximum 40-year term. When asked whether Silva hopes to get less than five years, Shapiro said, “I certainly hope so.”
The guilty plea makes Silva the fourth friend of Tsarnaev to be convicted on charges related to the aftermath of the explosions on April 15, 2013.
Three friends from University of Massachusetts Dartmouth were found to have entered Tsarnaev’s dorm room on April 18, 2013, shortly after photos of Tsarnaev and his older brother were made public by the FBI. Two have admitted playing a role in taking an incriminating backpack from the room and later disposing of it, while another was found guilty of lying about being with them on the night the backpack was taken.
Silva’s attorney emphasized that his client had nothing to do directly with the crimes allegedly committed by the Tsarnaev brothers.
“He’s not charged with having anything to do with the bombing,’’ Shapiro said.
Patricia Wen can be reached at firstname.lastname@example.org.