U.S. Attorney General Eric Holder authorized trial prosecutors to seek the death penalty for accused Boston Marathon bomber Dzhokhar Tsarnaev. Tsarnaev and his brother Tamerlan, 20 and 26 respectively, planted two pressure-cooker bombs at the marathon's finish line on Apr. 15, 2013.

"The nature of the conduct at issue and the resultant harm compel this decision," Holder said before the Friday deadline of the decision over whether to seek the death penalty.

Reuters reports: "Holder has said that he is not a proponent of the death penalty because he believes its value as a deterrent is questionable, but since becoming attorney general in 2009, he has authorized prosecutors to seek the death penalty in 36 cases."

"I'm not surprised by this decision," said Austin Sarat, Professor of Jurisprudence and Political Science at Amherst College, Massachusetts. "If the harm is unusual, if the harm is dramatic, gruesome, and devastating, it is often very hard for any other factor to outweigh it."

Tsarnaev's attorneys have argued against a death sentence on the grounds that he was following the lead of his older brother. They have also accused the government of using obstacles to hinder preparation of their client's defense.

57 percent of Boston residents favored life in prison for Tsarnaev, if he is convicted, with 33 percent in favor of execution.

The American Civil Liberties Union (ACLU) criticized the decision on the grounds that the case will be prosecuted in a state without the death penalty.

"This case now could easily last a decade," said Steve Huggard, a former federal prosecutor who is now Boston-based partner at Edwards Wildman. "This development will ensure that many of the victims feel like they are getting justice, but it will also extend and complicate the prosecution and dramatically increase the cost to taxpayers."