Will Boston jury sentence marathon bomber to death?

A day after a jury found Boston Marathon bomber Dzhokhar Tsarnaev guilty on all counts, the question foremost on the minds of victims is whether jurors will deliver a death penalty verdict.

While a Massachusetts poll last month favored life in prison over execution -- 62 percent to 27 percent -- legal experts say that's not a clear indicator of what 12 jurors will decide for 21-year-old Tsarnaev.

"That tells us a lot about what the population as a whole in Massachusetts thinks," said former prosecutor Troy Slaten. "But these 12 jurors during the voir dire process were death penalty qualified, which means that they were able to convince the judge and the prosecutor that, if push comes to shove, they'll be able to vote, if the law provides, for the death penalty in this case."

Tsarnaev was convicted Wednesday in the April 15, 2013, pressure-cooker bombings that killed three people and injured more than 260 near the Boston Marathon finish line. He was found guilty on all 30 counts, which included conspiracy and use of a weapon of mass destruction -- offenses punishable by death.

Tsarnaev's conviction was practically a foregone conclusion, given his lawyer's startling admission during opening statements that Tsarnaev carried out the attack with his now-dead older brother, Tamerlan -- though the defense argued Dzhokhar Tsarnaev fell under the influence of his radicalized brother.

In the next phase of the trial, the jury will hear evidence on whether Tsarnaev should get the death penalty or spend the rest of his life in prison.

A poll released March 23 by WBUR -- Boston's NPR news station -- found an overwhelming majority of Boston voters favored life in prison over execution. In contrast, an online national survey conducted after the guilty verdict Wednesday by NBC and SurveyMonkey showed Americans fairly divided over the sentence -- with 47 percent of those questioned wanting death, while 43 percent said they preferred life in prison.

One juror in the Tsarnaev trial had told the judge she is against the death penalty, but said she could consider imposing it.

"In order for the U.S. government to obtain a death sentence for Tsarnaev, there has to be a unanimous decision by the jury," criminal defense attorney Whitney Boan told FoxNews.com.

Aggravating factors -- such as deliberately placing the bomb near children -- play a critical role in the death penalty phase. Legal experts say aggravating factors must outweigh mitigating factors in the eyes of jurors in order to reach a death sentence.

Among those killed was 8-year-old Martin Richard, whose father said he watched helplessly as his son bled to death.

"There are a breath of aggravating factors in this case," said Slaten. "They had talked about this being a holy war and them being essentially jihadis and wanting to awaken the mujahadeen, which is the holy warriors in the United States."

"They looked at this as a war," he said of the Tsarnaev brothers.

Boan, however, said the defense will present several mitigating factors in an attempt to spare Tsarnaev death.

"They're going to present evidence from probably very highly qualified and experienced defense experts relative to the fact that Tsarnaev was 19 years old at the time this crime was committed."

She said the defense will likely point out that, "his frontal lobe was not fully developed yet" and that, "he's not thinking at the same level as someone who is a fully developed adult."

Both Slaten and Boan agreed it would be highly risky for the defense to place Tsarnaev on the stand.

"He could testify, but that exposes him to a very experienced prosecutor who will be allowed to then cross-examine him and talk about all the horrific things he's been convicted of," Slaten said.

Fox News' Gregg Jarrett contributed to this report.