BOSTON (AFP) - With jury selection barely begun in the trial of accused Boston marathon bomber Dzhokhar Tsarnaev, the prospect of the death penalty is already front and centre.
On Tuesday, as the day before, federal Judge George O'Toole repeated to prospective jurors that the trial "differs from many other criminal cases in a significant way. Mr. Tsarnaev is accused of crimes that are potentially punishable by a sentence of death.
"Under the law it is the responsibility of the jury, rather than the judge, to decide whether the defendant should be sentenced to death or life in prison."
The bombings killed three people and wounded 264 on April 15, 2013 near the finish line of the marathon.
Many legal experts believe Tsarnaev, 21, will be found guilty given the evidence against him: surveillance footage that places him at the crime scene with a backpack, his alleged hospital confession and a justification for the attack scrawled on the boat where he was found hiding and arrested.
"This case is not about guilt," Northeastern University law professor Daniel Medwed told NPR radio. "In my mind, this case is really about whether or not he's going to get the death penalty."
Twelve jurors and six alternates, selected from a pool of 1,200 potential jurors summoned this week, will decide if Tsarnaev is guilty and if so sentence him in a second phase of the trial.
The sentencing - the choice of death or life imprisonment - must be unanimous.
Each juror has to be "appropriate" for the case, the judge said again on Tuesday. In particular they have to be open to the death penalty but not determined to impose it all costs, either.
The state of Massachusetts, where Boston is the capital, abolished the death penalty in 1984.
No one has been executed in Massachusetts since 1947. In September 2013, a poll conducted by the Boston Globe newspaper found that 57 per cent of Bostonians support a life sentence for Tsarnaev, compared to 33 per cent who favour the death penalty.
Tsarnaev, a young Muslim of Chechen descent and a naturalised American since 2012, is accused of carrying out an act of terrorism with a weapon of mass destruction. The charge comes under federal law.
Attorney General Eric Holder announced last January that the government would seek a rare federal death penalty given that the offence was "especially heinous, cruel and depraved".
Ms Judy Clarke, a renowned specialist on the death penalty, is one of Tsarnaev's lawyers.
She has saved numerous clients from the gallows, such as Eric Rudolph, responsible for the Atlanta Olympic Park bombing in 1996; France's Zacarias Moussaoui, accused of complicity in the 9/11 attacks; and Jared Loughner, who shot dead six people and seriously wounded US Representative Gabrielle Giffords in Arizona in 2011.
All eventually pleaded guilty in exchange for life in prison.
Clarke will likely argue that Tsarnaev, who has been tense while hearing the judge instruct potential jurors, was influenced by his older brother Tamerlan, who was shot dead during a confrontation with police four days after the bombings.
But to get the death penalty off the table, Tsarnaev will need to cut a deal with prosecutors, which experts say would then need to be approved by the Justice Department.
Although a deal can be reached at any time, for now prosecutors do not seem interested.
Federal death penalty sentences are extremely rare in the United States.
There are 61 federally convicted prisoners on death row, compared to 3,054 sentenced at the state level, according to the non-profit Death Penalty Information Centre.
And actual federal executions are even rarer. There have been only four since 1963, including that of Timothy McVeigh in 2001 for the Oklahoma City bombings that killed 168 people and injured more than 600 in 1995.
The last was in 2003.