Twenty-four hours after the Tsarnaev jury was brought to tears by graphic, gruesome testimony describing the injuries to victims Martin Richard and Lingzi Lu, defense lawyers presented witnesses to show that someone other than Dzhokhar Tsarnaev planned this awful deed.   That someone other than Dzhokhar, they argued, was his brother Tamerlan.

And to convince jurors that the 21-year-old man sitting perpendicular to them in the courtroom was led by his brother,  the defense called on Elena Graff, a FBI fingerprint expert based at Quantico.  Professional and poised, Graff when asked about latent fingerprints on what was left of pressure cooker bombs set off on Boylston Street and she  identified them as Tamerlan’s.  When asked about fingerprints lifted from a soldering gun, a caulking gun, a note in Russian and multiple items found at the Tsarneav home in Cambridge, it was the same answer: The prints belonged to Tamerlan, she said.   But the FBI expert also found both brothers’ prints on an unexploded bomb in Watertown. And to a general question Graff agreed with the government that after an explosion there often are no detectable fingerprints.  Still, the defense after examining 500 bomb-related items scattered in wreckage along Boylston St, said the few prints that were found were Tamerlan’s.