BOSTON (AP) -- In the weeks after two bombs exploded near the finish line of the 2013 Boston Marathon, prosecutors charged three of the surviving suspect's friends with obstructing the investigation or lying to authorities.
More than a year later, they charged a fourth friend for deleting computer files and lying about certain details of his relationship with a second suspect.
As the first friend heads to trial this week, some defense attorneys and others are criticizing the extent to which federal prosecutors have charged the men, who are not accused of participating in the attack or knowing about it in advance.
Azamat Tazhayakov is charged with conspiracy and obstruction of justice for allegedly agreeing with another college friend, Dias Kadyrbayev, to remove Dzhokhar Tsarnaev's backpack from his dorm room after learning he was a suspect in the bombing, which killed three people and injured more than 260. Opening statements in his trial are scheduled for Monday in U.S. District Court.
Kadyrbayev, who faces a separate trial in September, is accused of throwing out the backpack, which contained fireworks that had been emptied of black powder, a bomb-making ingredient. Tazhayakov, according to an indictment, agreed with the plan to get rid of the backpack but did not participate in throwing it away. A third college friend, Robel Phillipos, is accused of lying to authorities.
"No matter what the facts are, I think the U.S. attorney's office may be a little overzealous in how harshly they are treating these cases," said Christopher Dearborn, a professor at Suffolk University Law School.
Defense lawyers have reserved their harshest criticism for the prosecution of the fourth man, Khairullozhon Matanov, a 23-year-old cab driver from Quincy who was charged in May.
Prosecutors say Matanov was a friend of Dzhokhar's brother, Tamerlan, who died in a shootout with police.
Matanov is accused of lying to the FBI, particularly about the contact he had with the Tsarnaevs after the bombings, including dinner at a restaurant the night of the attack and multiple phone calls that week.
Matanov is accused of deleting files on his computer after the FBI released the brothers' photos publicly three days after the bombing. He went to police the next morning and gave authorities their names, address and cellphone numbers. By that time, Tamerlan Tsarnaev was dead, and Dzhokhar was the object of a massive manhunt. He was later captured inside a boat in a Boston suburb.
Some defense attorneys have criticized the decision to charge Matanov.
"Most people, in the course of being subjected to an investigation and possible accusation, will sometimes say things that are not accurate but are nevertheless not criminal because they aren't material to the investigation," said Randy Chapman, a former president of the Massachusetts Association of Criminal Defense Attorneys.
Dearborn said he sees the charges against Matanov as "an attempt to impress the public."
"It's to send the message that we're tough on crime and very tough on terrorism, but at what price?" he said. "How does that resemble fairness?"
Others say prosecutors are not only justified but also have an obligation to charge anyone they believe impedes a terrorism investigation.
"Sometimes what happens is you end up with people who may not have had anything to do with the commission of the crime, but either lied or obstructed in the context of something that is extremely serious," said Gerry Leone, a former state and federal prosecutor who led the prosecution of shoe bomber Richard Reid.
"You charge them to send a message: You don't lie to investigators when they are trying to solve a terror investigation."
Professor Jeffrey Addicott, director of the Center for Terrorism Law at St. Mary's University School of Law in San Antonio, said the charges against the Tsaranev friends are typical in terrorism cases.
"This complaint is nothing new -- that the Department of Justice is being overzealous," he said. "On the other hand, the DOJ has been very trigger happy because they don't want another 9/11 or another Boston Marathon attack. Therefore, they are very aggressive in casting as big a net as possible."
The U.S. attorney's office declined to comment.