Defence wraps up case in Boston bombing trial

Lawyers for alleged Boston bomber Dzhokhar Tsarnaev quickly wrapped up their defense case on Tuesday as the four-week old trial entered its final stages.
Attorneys for Tsarnaev, who faces the death penalty if convicted of the April 2013 Boston Marathon attack that killed three people and wounded 264, called only four witnesses after prosecutors wrapped their case on Monday.
"That is all the witnesses that the defense will present," lawyer Tim Watkins informed the court following the testimony of an FBI fingerprint expert.
Jury deliberations are expected to begin swiftly following closing prosecution and defense arguments.
Tsarnaev's lawyers have already admitted the 21-year-old Muslim was responsible for the bombings, telling jurors in their opening statement: "It was him."
However the defense have sought to portray Tsarnaev's elder brother Tamerlan -- shot dead by police in the days following the attacks -- as the architect of the bombings, arguing that his younger sibling had fallen helplessly under his influence.
Under questioning Tuesday, FBI fingerprint expert Elaina Graff acknowledged that only Tamerlan Tsarnaev's fingerprints had been found on many items of evidence including materials used to manufacture bombs. Dzhokhar Tsarnaev's fingerprints were absent.
- Computer search clue -
A computer expert, Mark Spencer, meanwhile said that a search of the hard drives of three computers belonging to the Tsarnaev brothers had found more than five million documents.
Searches using terms including "Boston Marathon", "gun stores", "detonator", "fireworks firing system" were all carried out on a computer belonging to Tamerlan Tsarnaev, he said. No similar search terms had been found on Dzhokhar Tsarnaev's computer, the expert testified.
An entire issue of the Al-Qaeda propaganda magazine Inspire was found downloaded on Tamerlan Tsarnaev's computer, the expert added. The documents were later copied via a USB key and stored on Dzhokhar Tsarnaev's laptop, he said.
Spencer said the most popular pages visited online by Dzhokhar Tsarnaev prior to the bombings appeared to be Facebook and its Russian equivalent.
His brother meanwhile was visiting pages detailing how to make homemade bombs while watching online sermons by US-born Al Qaeda preacher Anwar Al-Awlaki, killed by a drone strike in Yemen in 2011.
On Monday, prosecutors closed their case with gruesome testimony about the youngest fatality in the bombings that left some jurors in tears.
Chief medical examiner Henry Nields recounted in graphic detail the injuries suffered by eight-year-old Martin Richard, who was torn apart by one of the pressure-cooker bombs planted by the brothers.
The child's blood-stained clothing was shown to jurors, some of whom were unable to hold back tears. The boy suffered a massive wound to the abdomen, along with burns.
Tsarnaev has pleaded not guilty to 30 charges over the attacks, the murder of a police officer, a carjacking and the shootout with police while on the run.
Seventeen of those charges carry the possibility of the death penalty under federal law.
If convicted, jurors will weigh whether to condemn him to death or life in prison without the possibility of parole, the only two sentencing options available.