Tsarnaev will not be tried as enemy combatant: What does that mean?

The suspect in the Boston Marathon bombings, Dzhokhar Tsarnaev, will not be treated as an enemy combatant and will face trial in a civilian, federal court, White House spokesman Jay Carney announced Monday.

In his hospital bed, the 19-year-old was charged with using a weapon of mass destruction, killing three people and injuring more than 200.

Carney's announcement contradicts calls from Sen. Lindsey Graham, R-S.C., and others for the government to place Tsarnaev in detention as an "enemy combatant" while questioning him about the bombing.

Enemy combatants do not have access to a lawyer while they're questioned, and in some circumstances can be tried by military tribunals. The courts haven't settled the question of whether a U.S. citizen arrested on U.S. soil could be treated as an enemy combatant, however. But to even have a shot at trying that approach, the government would need strong evidence showing a link between Tsarnaev and al-Qaida or other terrorist network. (Tsarnaev became a U.S. citizen in 2012.)

“You can’t hold every person who commits a terrorist attack as an enemy combatant, I agree with that,” Graham told The New York Times' Charlie Savage last weekend. “But you have a right, with his radical Islamist ties and the fact that Chechens are all over the world fighting with al-Qaida—I think you have a reasonable belief to go down that road, and it would be a big mistake not to go down that road. If we didn’t hold him for intelligence-gathering purposes, that would be unconscionable.”

Steve Vladeck, a law professor at American University, disagreed, saying it's legally "impossible" for Tsarnaev to be treated as an enemy combatant given that so far there's no evidence he is part of a larger terrorist network. Even if strong evidence did emerge, Tsarnaev's status as a U.S. citizen and that he was arrested in America, not abroad, would make it unlikely the government could hold him in military detention.

"Absent a clear, strong connection to al-Qaida, there's no legal authority to hold anyone," Vladeck said. "The U.S. government has no general authority to detain terrorism suspects without trial."

Two laws passed since the Sept. 11 attacks expanding the government's ability to detain terror suspects indefinitely and to try non-U.S. citizen terror suspects through the military court system. Since then, the government has used these laws to detain people arrested on U.S. soil in only two cases, and both suspected terrorists were eventually tried in civilian courts.

Military trials of terrorists so far have taken longer than civilian ones. Those accused of plotting the 9/11 attacks and killing 2,976 people—and who are being treated as enemy combatants—are still awaiting trial.

"There's nothing that's happened since 9/11 that calls the ability of civilian courts to handle terrorism cases into question," Vladeck said.

One legal technique that authorities are using to question Tsarnaev is something called the public safety exception.

Just an hour after police captured him in a Watertown backyard, the U.S. attorney in Boston, Carmen Ortiz, announced in a press conference that Tsarnaev would not be informed of his right to remain silent and to request a lawyer at the beginning of his interrogation. (He has since been advised of his Miranda rights.) A loophole established in a 1984 Supreme Court case allows police to question a suspect without first reading him his Miranda rights if they are asking questions that pertain to a public safety issue.

So, in the case of Tsarnaev, they could ask him if he knows of plans for a future attack, or if there are any more bombs hidden in the area, before ever telling him that his answers could be used against him in a court of law. (Police can always ask questions before reading Miranda rights, but then the suspect's answers would not be admissible in court. The public safety exception sidesteps that prohibition.)

Even though this technique was first used in a rape case (when police asked a man where he had hidden his gun), it's been used in terror cases since. Authorities questioned the Christmas Day "underwear bomber" Umar Farouk Abdulmutallab for 50 minutes without first reading him his Miranda warning, and also the attempted Times Square bomber Faisal Shahzad.

The Justice Department under Eric Holder has sought to expand this exception to cover questions that do not directly relate to an immediate threat, Emily Bazelon reported, but it's still unclear how that tactic would hold up if challenged in court.