The 21-year-old is facing 30 criminal counts in connection with the events surrounding the 2013 bombing, which left three dead and 260 others injured. Of those charges, 17 carry the death penalty.
His lawyers aren't disputing the fact that he did it.
Defense attorney Judy Clarke told the jury that Tsarnaev brought a pressure cooker bomb to the marathon and placed it at the finish line. He was there when a police officer was killed and also involved in a shootout with police.
"It was him," Clarke told jurors at opening statements earlier this month.
The defense's argument: that the then 19-year-old was influenced and enlisted by his older, self-radicalized brother, Tamerlan Tsarnaev, to commit acts of terror.
On Tuesday, one day after federal prosecutors rested after calling more than 90 witnesses
, defense lawyers rested their case without calling Tsarnaev to the stand.
An FBI fingerprint investigator testified about numerous pieces of evidence with Tamerlan's fingerprints but not Dzhokhar's. And a computer expert testified about online searches on Tamerlan's computer -- including gun stores, transmitters, fireworks firing system, detonator and Boston Marathon -- in the weeks before the bombing. Similar searches were not found on Dzhokhar's computer.
HEAR FROM TSARNAEV?
Tsarnaev will not be heard from in the guilt or innocence phase.
When an "it was him" strategy is presented on the first day, having the defendant testify doesn't make sense, said Sunny Hostin, former federal prosecutor and CNN legal analyst.
"This has never been a whodunit type of case," she said. "He has already admitted that he did it."
The benefit of putting a defendant like Tsarnaev on the stand would be to show remorse and gain sympathy of the jury, according to legal experts.
But putting the defendant up in the guilt or innocence phase allows cross examination from the prosecution, which can be hugely damaging to the defense.
Hostin said there are methods for conveying the defense argument made at the opening statements without putting Tsarnaev on the stand.
"You will want to put in testimony from his friends, his brother's wife. You almost want to build a character witness," Hostin said.
Even an anecdotal account to follow the defense's take on the trajectory of his upbringing could be beneficial, she added: "You want someone like a teacher to say 'he was a good student and then he moved in with his brother and then he changed.'"
ASSESS THE DEFENDANT
Thomas Ullmann, a law professor and Connecticut defense attorney who has worked on multiple capital cases, says a lawyer is constantly assessing, from day one, whether a defendant will make a good witness.
"It's not necessarily based on perception of guilt or innocence," Ullmann said, but rather how well they can communicate the defense.
Behind closed doors, defense attorneys are getting to know the client. They analyze how a defendant reacts to questions and responds to the legal team.
"One of the things you look for in a defendant in a death penalty case is remorse and an acceptance of responsibility," Ullmann said. "For Tsarnaev, his lawyers are looking for the duress of being under the influence of his older brother."
Hostin agreed, saying his lawyers will be gauging what he would say on the stand.
"If he is totally radicalized, gets on the stand and rather than plea for his life, says terrible things, he will die." Hostin said. "If he gets on the stand with any type of remorse and plays ball and says, 'He wanted me to do it. I don't believe any of those things,' then there is a slight chance."
Even if Tsarnaev never takes the stand, the jury will be affected by his body language throughout the trial, legal experts say.
"Jurors are looking the entire time," Ullmann said. "Some glare and stare at the defendant the entire trial."
"Body language is significant in a case like this. Juries watch everything that is happening from the lawyers to the defendant's demeanor," Hostin said.
Tsarnaev has been described as looking bored in court, without showing obvious emotion. He often sits staring ahead, slouched down in a chair, or resting his head on his hand and playing with his beard.
"I can't imagine that the jury hasn't been staring at him and trying to answer the question: 'Why would he do something like this?'" Hostin said. If he hasn't shown emotion during witness testimony, "It is going to be very problematic for him ... the jury is thinking, 'This is a cold-blooded killer.' "
If the jury hears from Tsarnaev at all, it will be in the penalty phase, in which the jury decides between the death penalty or life in prison, after a guilty verdict.
Ullmann said that testifying in the second phase allows for a separation for the jury. The evidence, photos, videos and emotional testimony will largely be behind and not brought up again.
"Once you separate the two phases, it becomes clear: guilt isn't an issue. It's whether he should die or spend life in prison." Ullmann said. "It is a very different analysis for the jury."
Hostin said the strategy for hearing from Tsarnaev in the second phase would be to have him connect with one person on the jury and build sympathy.
"You want to show him as a kid going to school in the United States, somewhat Americanized, that will be in line with the jurors who have children," Hostin said. "You want them to think, 'What happens if my kid gets in with the wrong crew?'"
In capital cases, just one juror who does not think the defendant deserves the death penalty can allow the defendant to live.
Ultimately, the decision to put Tsarnaev on the stand will be made by his legal team.
Clarke, one of the most famous defense attorneys in the country, has represented defendants in notorious cases.
Clarke's first capital case was defending Susan Smith, an emotionally disturbed South Carolina mother who strapped her two boys into her car and let them roll into a lake, drowning them. The jury spared Smith's life.
Ullmann said defense attorneys look up to Clarke.
"She is known for getting to know her clients very well," Hostin said. "She is very affectionate and becomes a mother figure for clients."
"If you have a trusting relationship with your client and build up integrity, when it comes time to advise someone, you want the defendant to follow your advice," Ullmann said.
Clarke has also defended Ted Kaczynski, also known as the Unabomber; Eric Rudolph, the man responsible for the 1996 Olympics bombings in Atlanta; Zacarias Moussaoui, the 9/11 conspirator; and Jared Lee Loughner, the Arizona man whose deadly shooting rampage wounded former U.S. Rep. Gabrielle Giffords.
All those cases were settled through plea bargains that took the death penalty off the table, before the jury could ever hear from the defendants.
Said Hostin: "If you're facing the death penalty, you want Judy."