As they try to keep their client from receiving a death sentence, Dzhokhar Tsarnaev's attorneys have a major challenge.

They've acknowledged that he helped carry out the Boston Marathon bombings. And Judge George O'Toole says they can't play up the influence of Dzhokhar's deceased older brother Tamerlan until the trial's sentencing phase. How, then, to call the prosecution's narrative into question? The answer: focus on technology. Wednesday, defense attorney Miriam Conrad disputed the prosecution's account of cell-phone calls placed by the Tsarnaev brothers — arguing, basically, that they might have been shorter than the prosecution claims.

Tuesday it was Twitter — with Conrad casting the FBI's investigation into Dzhokhar's social-media habits as slipshod. It's a method that lets the defense challenge the prosecution's credibility — without engaging victims or their families and friends in an adversarial way. Of course, whether it will sway the jury remains to be seen.

The prosecution says Dzhokhar Tsarnaev posted using this Twitter account: