In an unusual opening statement this morning Judy Clarke, whose client Dzhokhar Tsarnaev is pleading not guilty to charges he bombed the 2013 Boston marathon, told the jury, “It was him.”

“You might say, ‘Why a trial?’” said Judy Clarke. “The indictment in that case is not that simple.”

Tsarnaev faces 30 charges related to the bombing and its aftermath. Clarke argued her client is innocent of some of the conspiracy charges and murdering MIT police officer Sean Collier.

But despite Judge George O’Toole’s objection to including what he ruled was mitigating evidence in the opening, the brunt of Clarke’s argument focused on Dzhokhar’s dead brother, and alleged co-conspirator, Tamerlan.

Tamerlan was 26 years old and Dzhokhar was 19 at the time of the attack.

Clarke held up a photo of Tamerlan with her defendant when Dzhokhar was a child. Tamerlan, a former Golden Gloves boxing champion, who his mother once adoringly called “Hercules,” had his arm wrapped around a young, smiling Dzhokhar, dwarfing the defendant with the shear bulk of his size.

“It was Tamerlan Tsarnaev who radicalized, it was Dzhokhar who followed him,” she argued.

It’s a defense that has worked before.

It worked less than 15 years ago in a similarly high-profile case, for a man who helped commit an atrocity that left 10 innocent people dead and threw a major American metropolitan area into a weeks-long panic.

Lee Boyd Malvo and John Allen Muhammad were convicted of murdering 10 people in the 2001 “Beltway sniper case.” Malvo was 17, his co-conspirator was in his 40s.

Muhammad was sentenced to death, Malvo’s life was saved.

The argument Malvo’s lawyer, Craig Coolidge, made sounded much the same as Clarke’s.

“This is a case of indoctrinization, and the evidence in this case is going to show you a degree of indoctrinization and incredible influence,” he told the jury.

In his argument, Coolidge cited a 2000 FBI report, “Project Megiddo,” which examines terror attacks and cultish methods of manipulation. The report shows how extremists are able to convince people to commit horrific acts they would typically find objectionable.

“Our case was a case study of how one person could manipulate another,” he told The Daily Beast.

In Tsarnaev’s case, Clarke credited his older brother with buying ammunition, backpacks, and a Russian language guide to building a bomb.

“Tamerlan led the way down Boylston Street,” she said. “Tamerlan shot Sean Collier.”

She argued the defendant became increasingly vulnerable to the brother he “loved” once his parents moved out of the country and his grades started to flounder. Tamerlan’s was a “special kind of influence dictated by his age, his culture, and his special force of personality.”

He achieved this feat through mental manipulation alone, argued Clarke. “The evidence will not establish and we will not argue that Tamerlan put a gun to Dzhokhar Tsarnaev’s head, or forced him to join in the plan, but you will hear evidence of the kind of influence,” she said.

Anticipating this argument, prosecutor William Weinreb told the court the defendant was motivated by his own radical believes, not his brother’s.

“He did it because it advanced a cause he believed in, and he did it because he thought it would secure him a place in paradise,” he said.

Weinreb told the court the younger Tsarnaev read terrorist writings, listened to terrorist lectures, and used a dual identity online to spread his radical beliefs. He cited a note Tsarneav allegedly wrote in pencil while he was hiding from police in a beached Watertown boat, where he said he wished he’d become a martyr like his brother.

Weinreb told the court that the defendant was under the impression that, for him, bombing was a “victory in a holy war.”

There is a hole in the Weinreb’s argument, however. The defense pointed out that there is no evidence that Dzhokhar downloaded this material himself. In fact, they argue that the government has no knowledge of Tamerlan downloading the material either. The documents trace back to a thumb drive “that has not been found.”

Yet, without evidence that Tamerlan put a gun to his younger brother’s head and forced him to plant the bombs, the not-guilty argument—even to the conspiracy charges—is weak.

The defense likely knows this. But if Dzhokhar is found guilty, he’ll face the death penalty in the sentencing phase. If the jury sentences him to death, because of complications related to selecting a jury in the region Dzhohkar allegedly attacked, pleading not guilty may lead the way to an appeal down the road.

Clarke isn’t going to miss a chance to save his life in the opening and there is a chance this argument may do just that—even in the sentencing phase.

The problem for Tsarnaev is, in Malvo’s case, the strength of Coolidge’s argument rested upon solid first-person testimony.

“We had very strong civilian witnesses who had watched the process,” he said. “One person testified how Muhammad was able to train Malvo to ‘overcome the hesitation to shoot the human form.’”

That’s a stark contrast from the now-21-year-old Tsarnaev, for whom defense witnesses may be hard to find. In pretrial hearings the defense revealed their struggle in finding people to testify.

Another problem for the defense is much of Dzhokhar’s radicalization appears to have occurred in private.

“He had a side to him that he kept hidden, even from his closest friends,” said Weinreb.

The prosecution revealed a few new and potentially damning details about the case. Murdering people, the prosecution alleges, apparently gives Dzhokhar the munchies. Twenty minutes after the bombs were set off, the government says the defendant was caught on surveillance going to a Cambridge Whole Foods to buy milk. After allegedly murdering Sean Collier he swung by a convenience store to pick up snacks.

“He takes his time. He’s not concerned,” said Weinreb of the video he plans to show the jury. “He makes sure he gets exactly what he wants.”

The government also lined up the case for pinning the death of MIT officer Sean Collier on the defendant too. For the first time, prosecutors revealed that there was a witness who saw Tsarnaev by the officer’s cruiser, and that investigators found blood that matched Collier’s DNA on gloves and a key chain in the brothers’ Honda Civic.

But if Clarke’s argument was made in anticipation of the sentencing part of the trial, the government’s was too. The government will have to convince every single juror to sentence the him to death. To do that, they will have to pull on their emotional heartstrings.

The government delved into graphic details at every chance they got. The deaths of the three bombing victims—23-year old Lu Lingzi, 29-year old Krystle Campbell, and 8-year old Martin Richard—were described in vivid detail.

“The bomb tore large chunks of flesh out of Martin Richard’s body,” said Weinreb, describing how his mother, made half-blind, watched helplessly as her child died.

After the explosion, Lingzi saw her “insides were coming out of her stomach, so she used her hand to push them back in,” said Weinreb. And Campbell held on to the hand of a friend, “tight as the life drained out of her body.”

The prosecution is banking on those details being too gruesome for a jury to let Dzokhar Tsarnaev live—radicalized by a monster or not.