This past Tuesday, a federal jury in Boston found Robel Phillipos guilty on two counts of making false statements to federal investigators. Phillipos was a friend of Dzhokhar Tsarnaev, who is accused of planting bombs near the finish line of the Boston Marathon with his brother last year. F.B.I. agents had interviewed Phillipos five times; the first four times, he denied that he had been in Tsarnaev’s dorm room on April 18, 2013, three days after the bombing. He also denied knowing that his friends had removed some items from the room, although he had been in the room and knew that items were removed. There was no allegation that Phillipos in any way aided the bombing itself. Still, with the conviction, Phillipos faces up to eight years in prison on each count.

Tsarnaev’s own trial for his part in the marathon bombing, which killed three people and injured hundreds, is not scheduled to begin until next year, but the Boston court has, since June, been hearing the cases of three of his best friends: Phillipos, Dias Kadyrbayev, and Azamat Tazhayakov. (Tsarnaev’s older brother Tamerlan died from injuries suffered while he attempted to escape from police.) Kadyrbayev and Tazhayakov, both students from Kazakhstan, were each charged with conspiracy to obstruct justice and obstruction of justice, for “agreeing to knowingly alter, destroy, conceal, and cover up tangible objects belonging to Dzokhar Tsarnaev.” Tazhayakov pleaded not guilty and was convicted by a jury, in July. At a sentencing scheduled for mid-November, he faces up to twenty-five years in prison. Kadyrbayev pleaded guilty, in August, in exchange for the U.S. attorney’s recommending a prison sentence of no more than seven years, though the federal judge in Boston could opt for a longer term when he sentences him later this month.

The evidence presented in court during each of these proceedings, which were heard over the past several months by Judge Douglas Woodlock, has given a fairly consistent picture of the sequence of events beginning in the early evening of April 18, 2013. Kadyrbayev and Tazhayakov lived together in an apartment in New Bedford, near the campus of the University of Massachusetts Dartmouth. They met Tsarnaev during the 2011–2012 school year, when they were all freshmen. Phillipos, also a student at UMass, is from Cambridge, Massachusetts, where he had attended Cambridge Rindge and Latin high school with Tsarnaev. The four of them spent a great deal of time together, most often at the Kazakh students’ apartment, getting stoned on weed supplied by Tsarnaev—all except Tazhayakov, who was known as a mama’s boy, even though he was thousands of miles away from home.

At 5 p.m. on April 18th, the F.B.I. released pictures of the suspected perpetrators of the bombing, lifted from a surveillance tape, and asked for help identifying the suspects. As soon as he saw the first, grainy picture on the news, Kadyrbayev texted his roommate to urge him to come home. Once Tazhayakov arrived, they drove to campus, where they rushed to Tsarnaev’s room in Pine Dale Hall. So did many other students, whose first reaction to the pictures was not to call the authorities but to go ask Dzhokhar himself if he had set off the bombs. Kadyrbayev had even texted Tsarnaev, asking as much: “for real?” Without confirming or denying that he was the bomber, Tsarnaev replied, “If yu want yu can go to my room and take what's there,” accompanied by a smiley face.

The door to Tsarnaev’s room, which he shared with a studious engineering major named Andrew Dwinells, was locked. Students milled around for a bit, exchanged questions and expressions of concern, then left. Tazhayakov and Phillipos, who had shown up with another friend, went to someone else’s room and started playing video games. Kadyrbayev found Dwinells studying in a nearby common area, showed him Tsarnaev’s message, and asked to be let into the dorm room. Dwinells opened the door for him and waited on his side of the room, which was very neat, while Kadyrbayev conducted a search of Tsarnaev’s side, which was quite messy.

About ten minutes in, Tzahayakov and Phillipos came to the room, having been summoned by a text message by Kadyrbayev. They sat down to watch a movie. Kadyrbayev continued to search the room for another twenty minutes. When the three of them left, Kadyrbayev was carrying the following possessions of Tsarnaev’s: a Sony Vaio laptop computer, a thumb drive, a bag of marijuana, a baseball cap, an ashtray, and a backpack that contained some hollowed-out fireworks and a half-empty jar of Vaseline. Two witnesses have testified that Kadyrbayev said that he thought the fireworks and Vaseline had been used to make the bombs.

The three of them went to Taco Bell, then to Tazhayakov and Kadyrbayev’s apartment, where Kadyrbayev’s girlfriend, Bayan Kumiskali, was about halfway through watching “The Pursuit of Happyness.” Everyone but Tazhayakov got stoned, then they all sat on the couch and watched the second half of the movie, checking for news on their devices. When the movie ended, Kadyrbayev and Kumiskali retired to a bedroom. At some point Tazhayakov dozed off; later, so did Phillipos.

When Tazhayakov awoke early the next morning, he discovered that Dzhokhar Tsarnaev, who was still on the loose, had now been publicly identified as a suspect in the bombing, and that Tamerlan had been killed. Tazhayakov began to panic and smoked marijuana for what may have been the first time in his life. At some point, Kadyrbayev told Kumiskali that he had removed some items, including the emptied-out fireworks, from Tsarnaev’s dorm room. She told him that the items might be evidence and that she did not want them in the apartment. Kadyrbayev went into the living room, where Tazhayakov and Phillipos were, and said that he thought he should get rid of the backpack. Tazhayakov agreed, according to testimony that he gave during Phillipos’s trial after he himself had been convicted. In his confession to the F.B.I., Phillipos said that he had said, “Do what you have to do”; he did not testify at his own trial, but his lawyers claimed that he never discussed the backpack with Tazhayakov or Kadyrbayev. (In fact, they claimed that the F.B.I. confession was not written by Phillipos himself—a claim that did not sound incredible because the document was full of obvious inaccuracies.) Kadyrbayev took the bag outside and threw it in a Dumpster.

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When the government’s lawyers and the two defense teams offered their accounts of these events at the trials of Phillipos and Tazhayakov, they differed on one factual point: the U.S. government, in its case against Robel Phillipos, contended that when Kadyrbayev came out of the bedroom and said that he thought he should throw out the backpack—a key element of the conspiracy charges against the Kazakhs—he was speaking English; Phillipos’s lawyers say that Kadyrbayev was speaking Russian, which Phillipos does not understand. Kadyrbayev has not testified at either trial; Tazhayakov, who, after he was convicted, agreed to testify against Phillipos in the hopes of getting a more lenient sentence, said that the language spoken was English, but the defense marshalled a series of witnesses who said that, as a rule, the two Kazakh men spoke Russian to each other. The language issue concerned only one of many counts included in the charges against Phillipos, and the jury ultimately found him not guilty of lying to investigators about having engaged in a discussion of whether to throw out the backpack. The point of disagreement, and the exclusion of the relevant count by the jury, will ultimately have little or no impact on Phillipos's sentence. But the detail raises an important question: Why did Phillipos and Tazhayakov face different charges in the first place?