AP
A court sketch of Dzhokhar Tsarnaev.
This seems like a counterintuitive move made by Dzhokhar Tsarnaev's attorney, Judy Clarke, one of the top death penalty lawyers in the US. But the not guilty plea is part of her larger strategy to get her client a more lenient sentence.
This strategy worked when Clarke defended Jared Lee Loughner, the gunman who in 2011 shot nearly 20 people at a Tucson, Arizona supermarket, including then-Rep. Gabrielle Giffords. After initially pleading not guilty, Loughner agreed to a deal that took the death penalty off the table.
Legal expert and Ohio State University
Tsarnaev's not guilty plea isn't necessarily a claim of innocence, but rather an expression that the defense wants to hold the government to its burden of proof in the case, Berman explained. And once the prosecution lays out its case, the defense will be better informed on how to argue against a death sentence in the penalty phase.
"[The defense] wants to see how the government is going to put its case together, who the witnesses are, what kind of arguments they make about the defendant," Berman said.
"The best way to do this is to have this trial phase where the government is going to put forward all of its evidence, which is not just about guilt but why the death penalty is appropriate, and then the defense has essentially a preview and can then start from the get-go on developing a corresponding, much more informed strategy for the penalty phase."
By entering a not guilty plea and going through a trial, the defense gets a look at how the prosecution is going to build a case against Tsarnaev. It also gets to see how the jury will react to the defense's own strategy.
"In so many ways, it's not just what's forced the government to show their hand, it's also 'let's make our point before the main event and see how the jury seems to be responding and what kind of reactions we think we're getting from the judge and the jury as we put forward a variety of suggestions," Berman said.
Clarke's admission that her client did participate in the bombing could also be a strategic move, allowing her to build credibility with the jury and make them feel like they can trust what she says.
AP Photo/The Lowell Sun & Robin Young, File
This combination of undated file photos shows Tamerlan Tsarnaev, 26, left, and Dzhokhar Tsarnaev, 19.
Since there isn't much of a question of whether Dzhokhar helped carry out the plot, the defense will likely now focus on diminishing his role and emphasizing the part played by his now-deceased older brother Tamerlan.
On the first day of the trial, Clarke held up two photos of the brothers - one from years before the marathon attack and the second from the scene of the bombing where they're shown carrying backpacks containing explosives, according to the AP. She then asked the jury: "What took Dzhokhar Tsarnaev from this ... to this?"
There's also still potential for Tsarnaev to seek a plea deal down the line, like Loughner did.
"Maybe it's a hope on the part of the defense that if they go through the guilt phase, the government will see that they'll have a challenge getting a death sentence," Berman said. "... Given that there's no doubt about guilt and a life sentence is pretty likely regardless, I'm sure the defense is at every stage saying [to the prosecution], either directly or indirectly, is this really worth all your time and energy?'"
Dzhokhar, 21, has been charged with planting two bombs near the finish line of the Boston Marathon in 2013. The attack killed three people and injured more than 200 others. His older brother Tamerlan, whom the defense appears to be portraying as the mastermind behind the bombing, died in 2013 during a manhunt for the brothers in Watertown, Massachusetts.