Boston Marathon Bomber’s Death Sentence Is Thrown Out by Court

Liz Norden, the mother of two men who lost legs in the bombings, said the decision was a bitter disappointment.

“If this case didn’t deserve the death penalty, what would?” she said. “He admitted to it. His attorney admitted to it. I’m in disbelief.”

A spokeswoman for U.S. Attorney Andrew E. Lelling’s office said prosecutors were reviewing the opinion and had no comment. Prosecutors could ask for a hearing from the full appeals court or go to the U.S. Supreme Court.

But George Vien, a former federal prosecutor, said the appeals court seemed to hold Judge O’Toole, whom he called a “very experienced and conscientious judge,” to an impossible standard.

He said the judges applied the Patriarca rule “in a way that required something close to perfection,” which he said was not the standard in jury selection. “The idea that he is going to be able to pick a jury and monitor all their Twitter feeds is ridiculous, and it’s unrealistic.”

The backpack bombings near the finish line of one of the world’s most famous races killed three people and injured 260 more, many of them grievously. Seventeen people lost limbs. A fourth person, a law enforcement officer, was killed as Mr. Tsarnaev and his older brother, Tamerlan, fled a few days later; Tamerlan died in a shootout with the police.

At the appeals hearing in December, Mr. Tsarnaev’s team zeroed in on Judge O’Toole’s decision not to further question two jurors who had failed to disclose tweets and Facebook posts about the crime.