BOSTON — After questioning just four witnesses over five hours, the defense for Dzhokhar Tsarnaev in the Boston Marathon bombing trial rested its case on Tuesday.
The scant defense was dwarfed by the prosecution’s roster of 92 witnesses over 15 days. And it reflected the defense strategy of admitting at the outset that Mr. Tsarnaev had indeed participated in the 2013 bombings, which killed three people and injured more than 260 others.
That admission of guilt had the predictable effect of curtailing the case that the defense could put on in this first phase of the trial. Its four witnesses spoke to a narrow range of physical evidence, like Internet searches and a lack of fingerprints, that the defense suggested showed its client was less culpable than his older brother, Tamerlan. The brother died after a shootout with the police and after Dzhokhar drove over him in a getaway car.
While Mr. Tsarnaev’s lawyers have admitted his guilt, he has not pleaded guilty. And so lawyers for both sides are preparing to make their closing arguments Monday to the jury, which is all but certain to convict him on most or all of the 30 charges against him.
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Boston Bombing Trial, Week by Week

Seventeen of those charges carry the possibility of the death penalty. They include conspiracy to use a weapon of mass destruction resulting in death, possession and use of a firearm during and in relation to a crime of violence resulting in death, and conspiracy to bomb a place of public use resulting in death.
Assuming they find him guilty of at least some of the death penalty charges, the same jurors will return for the second phase of the trial, in which they will determine whether to sentence Mr. Tsarnaev, 21, to prison for the rest of his life or condemn him to death.
The defense is as determined to save his life as the prosecution is to see him executed. So the defense is preparing to make its major arguments during the sentencing phase, when it will present what it says are mitigating factors that should spare Mr. Tsarnaev from the death penalty — he was 19 at the time of the bombings, for example, and had no criminal record.
And perhaps most important, the defense intends to argue that at a time when he was lost and flunking out of school, Mr. Tsarnaev fell under the influence of Tamerlan, a violent Islamist extremist who bullied him into going along with the bombings.
To that end, the defense focused its short case Monday and Tuesday on trying to show Tamerlan as the mastermind of the crime. One witness, Mark Spencer, a digital forensics expert, testified that Tamerlan’s laptop contained searches for “detonator,” “transmitter and receiver,” and “fireworks firing system.” He said that Dzhokhar’s laptop had no such searches and that he had spent his computer time on Facebook and a Russian social media site.
The prosecution has argued that the Tsarnaev brothers were full and equal partners. During cross-examination, the government established that without a video camera, it would be impossible to tell who was using a computer at any given time. And it established that before the bombing, Dzhokhar’s computer was used to search various jihadist terms, including “Jannah Al Firdaus,” referring to paradise. Later, his computer was used to search articles about the bombing and for “blackhead removal.”
Another defense witness, Elaina Graff, an F.B.I. fingerprint examiner, said she had found Tamerlan’s fingerprints at the bomb scene on Boylston Street but not Dzhokhar’s. She also said, however, that she had found two sets of Dzhokhar’s fingerprints on a plastic container holding three pounds of explosive powder, and six sets of his brother’s prints on the same container.
Under cross-examination, Ms. Graff said some of the bomb components and the backpacks in which they were carried had no prints at all. “Fingerprints are very fragile,” she said, noting they could be wiped off, be smudged or even evaporate.
William Weinreb, the lead prosecutor, suggested that the absence of prints was meaningless because “the bombs didn’t build themselves, the backpacks didn’t carry themselves.” He added, “The presence of fingerprints tells you he touched it, but the absence of a person’s fingerprints doesn’t tell you whether he did or didn’t touch it.”
After the defense rested its case, the judge, George A. O’Toole Jr. of Federal District Court, told the jurors to return Monday for closing arguments and to begin deliberations.
He also reminded the jurors, who are not sequestered, not to say anything about the case to anyone, “including to yourself in the mirror.”
“People will want to know things,” he said, but “you can’t tell them.”
“Nothing. Please,” he added.