By Elizabeth Barber

BOSTON (Reuters) - The jury in the Boston Marathon bombing trial on Tuesday concluded its first day of deliberations without reaching a verdict on whether Dzhokhar Tsarnaev, is guilty of the 2013 attack that killed three people and injured 264 others.

Tsarnaev, 21, is also charged with shooting a police officer to death three days after prosecutors contend he and his older brother set of a pair of homemade pressure-cooker bombs at the race's crowded finish line on April 15, 2013.

The question of whether the ethnic Chechen defendant is guilty of 30 criminal counts may be the easy part of the jury's job. If they find him guilty, the same 12 jurors will hear a second round of evidence before determining whether to sentence Tsarnaev to death or to life in prison without possibility of parole.

Defense lawyer Judith Clarke readily admitted her client's responsibility on Monday but contended that 26-year-old Tamerlan Tsarnaev had been the driving force behind the attack. Tamerlan died early on April 19, 2013 after his brother ran him over with a car at the end of a gunfight with police.

Representatives of the Roman Catholic Bishops of Massachusetts distributed flyers outside court on Tuesday reiterating the church's opposition to capital punishment.

"The defendant in this case has been neutralized and will never again cause harm," read the statement, signed by Cardinal Sean O’Malley of Boston and three bishops. "Society can do better than the death penalty."

Though the death penalty is unpopular in Boston, a liberal-leaning city with a deep-rooted Catholic community, jurors who serve on federal capital murder trials must express a willingness to impose it. It took the court 24 days to choose 12 jurors and six alternates who satisfied that condition.

Prosecutors called 92 witnesses over the last month to make the case that Tsarnaev was an equal partner with his brother in plotting the bombings as vengeance for U.S. military campaigns in Muslim-majority countries. The defense called just four witnesses, including an FBI photographer who also testified for the prosecution.

The blasts killed restaurant manager Krystle Campbell, 29, Chinese exchange student Lingzi Lu, 23, and 8-year-old Martin Richard. Tsarnaev is also accused of the fatal shooting of Massachusetts of Institute of Technology police officer Sean Collier, 26.

(Editing by Scott Malone)