BOSTON (Reuters) - This city’s deepest wound - the 2013 Boston Marathon bombings that killed three and injured hundreds more - will be re-examined Thursday when lawyers for bomber Dzhokhar Tsarnaev seek to have his death sentence lifted because the jury pool was too traumatized to render a fair verdict.

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The then-19-year old Tsarnaev and his 26-year-old brother Tamerlan sparked five days of panic in Boston that began April 15, 2013, when they detonated a pair of homemade pressure cooker bombs at the race’s packed finish line. The pair eluded capture for days, punctuated by a gunbattle with police in Watertown that killed Tamerlan and led to a daylong lockdown of Boston and most of its suburbs while heavily armed officers and troops conducted a house-to-house search for Dzhokhar.

Tsarnaev’s defense team, in briefs filed with the 1st U.S. Circuit Court of Appeals in Boston, argued that the unprecedented shelter-in-place order biased the pool of potential jurors, including one actual juror who joined the unanimous vote for the death penalty.

The manhunt for the younger Tsarnaev, now 26, left an indelible mark on the city. Armored vehicles and thousands of National Guard troops cast a dragnet across the Boston suburb of Watertown. Just before a resident found a wounded Tsarnaev hiding in a boat parked in his backyard, a broadcast of a Boston police scanner channel attracted nearly 265,000 listeners.

“Even if a juror honestly believes before trial that he or she can objectively hear the evidence, when a community has been aroused to a fever pitch, the prospective juror may come to fear returning to neighbors with anything other than a guilty verdict and a death sentence,” Tsarnaev’s defense team wrote in a legal brief.

U.S. Justice Department lawyers disagreed, saying Tsarnaev received a fair trial. The department has noted a survey conducted for Tsarnaev’s own lawyers found 96.5% of respondents in Washington, his preferred venue for the trial, had heard of the bombings.

But legal experts say arguing that some jurors were tainted with bias may offer the defense team its best bet in winning relief from the court. The defense and prosecution each will get an hour to argue their side before an appellate panel of judges.

“Of course, (the defense) will throw in the kitchen sink, the bedroom furniture and everything else in hoping something sticks,” said Robert Bloom, a professor at Boston College Law School. “That is what you do in these cases.”

The defense team says the trial should not have been held in Boston, that some jurors made false statements before their selection, and that the jury should have heard that Tamerlan had been a suspect in a 2011 triple homicide.

A friend of Tamerlan admitted to the FBI having committed the murders with him, according to recently unsealed court documents. The jury did not hear about those murders during the trial.

The younger Tsarnaev was sentenced to death in 2015 after a jury found him guilty of killing three people: Martin Richard, 8; Chinese exchange student Lingzi Lu, 26, and restaurant manager Krystle Campbell, in the bombing; as well as murdering Massachusetts Institute of Technology police officer Sean Collier, 26, three days later as the brothers attempted to flee the city.

Before the bombings, the younger Tsarnaev had no record of serious criminal offense. But Tamerlan was aggressive, domineering and likely homicidal before driving his younger brother to join him in carrying out the bombings, according to the defense team’s line of reasoning in court papers.

Tsarnaev’s defense team also says the jury’s foreperson falsely denied, during the selection process, calling Tsarnaev a “piece of garbage” on Twitter. That juror lived in Dorchester, the same neighborhood as the attack’s youngest victim, according to defense team legal briefs.

During the trial, Richard’s family asked U.S. prosecutors to consider taking the death penalty off the table. They said the death penalty could bring years of appeals and prolong reliving the most painful day of their lives, according to a letter published in the Boston Globe newspaper. A poll by the Globe also showed that about two-thirds of Massachusetts residents favored a life sentence for Tsarnaev.