Boston Marathon bomber Dzhokhar Tsarnaev's death sentence overturned by appeals court

Even though he and his brother caused "battlefield-like carnage" when they bombed the Boston Marathon in 2013, Dzhokhar Tsarnaev's death sentence must be vacated pending a new penalty-phase trial, a federal appeals court said Friday.

Friday's decision means that the Tsarnaev's death sentence is vacated and that three of his convictions are reversed.

Tsarnaev and his elder brother Tamerlan, both Kyrgyz-American nationals of Chechen descent, planted bombs close to the finish line of the Boston Marathon on 15 April 2013.

In its ruling, the court said the trial judge had failed to exclude jurors who had already concluded that Tsarnaev was guilty.

The U.S. District Court now must enter judgments of acquittal on the relevant charges, empanel a new jury and preside over a new trial limited to what penalty Tsarnaev should get on the death-eligible counts.

The 1st Circuit said the "pervasive" media coverage featuring "bone-chilling still shots and videos" of the bombing and dayslong manhunt required the judge to run a jury selection process "sufficient to identify prejudice". The ruling found that the presiding judge in Tsarnaev's 2015 trial "did not meet the standard" of fairness.

The three appeals judges found that two jurors in Tsarnaev's sentencing were biased against him before the trial started, citing social media posts introduced by Tsarnaev's lawyers. The appeals judges, in a hearing on the case in early December, devoted a significant number of questions to the juror bias argument.

Tsarnaev's lawyers say one of the jurors, who would go one to become the jury's foreperson, or chief spokesperson, published two dozen tweets in the wake of the bombings.

The judges noted that the Boston court has a longstanding rule obligating such an inquiry.

One juror had said in Twitter posts that that she was "locked down" with her family during the manhunt and retweeted another post calling Tsarnaev a "piece of garbage", but later told the court she had not commented on the case or been asked to shelter in place, the defense said. He's been serving his sentence in a high-security supermax prison in Colorado.

Tsarnaev was sentenced to death in 2015 for his part in the 2013 Boston Marathon bombing, which took the lives of at least three people and seriously injured hundreds more.