BOSTON — Defense attorneys for Boston Marathon bombing suspect Dzhokhar Tsarnaev resumed efforts to distance him from the planning of the attacks as they began their first full day of defense testimony Tuesday in Tsarnaev’s trial.

The 21-year-old is charged in the April 15, 2013, attack that left three people dead and more than 260 injured. He faces 30 counts, including 17 that could carry the death penalty.

Tsarnaev’s attorneys have all but conceded the most serious charges — in her opening statement, lead attorney Judy Clarke said Tsarnaev was involved in carrying out the attack. “It was him,” Clarke told the jury. But the defense contends that he was under the influence of his older brother, Tamerlan, who was killed during a police shootout four days later.

On Tuesday morning, computer forensic consultant Mark Spencer testified that he had examined hard drives on two computers: a Sony Vaio laptop that belonged to the defendant, as well as a Samsung belonging to Tamerlan.

About a week before the bombings, he testified, the older brother’s Samsung showed search records for a series of bombing-related terms: “gun store,” “detonator” and “fireworks firing system” among others. Dzhokhar’s Sony showed no searches for those terms prior to the bombings, Spencer said. He also found bombmaking instructions on the Samsung, but not on the Sony.

Spencer explained how material from Complete Inspire, an Internet magazine of al-Qaeda in the Arabian Peninsula, wound up on the Sony. He said it got there via a thumb drive that had been used to carry files from Tamerlan’s Samsung.

The digital trail “would appear to indicate the Complete Inspire PDF was copied from the Samsung laptop and then copied to the Sony laptop,” Spencer said. The transfer took place in January 2012, as Tamerlan was preparing to leave for six months in Russia, where he allegedly trained for jihad among Islamic militants.

Asked if Dzhokhar’s Sony might have downloaded the Complete Inspire document directly from the Internet, Spencer answered, “No.”

During cross-examination, Assistant U.S. Attorney Aloke Chakravarty raised the prospect that computers might have been shared within the family. Spencer said a Hewlett-Packard desktop at the Tsarnaev home contained a wide range of material, including children’s content as well as information he understood to be jihadist.

“You can’t tell who’s actually using a computer at any given time,” Chakravarty suggested.

“Generally speaking, that’s fair to say,” Spencer said.

Spencer also confirmed that search terms found on Dzhokhar Tsarnaev’s Sony on the weekend before the bombings included “the call of jihad.”

But a few minutes later, Tsarnaev’s team called Elena Graff to the witness stand. An FBI fingerprint expert who led the team that examined more than 800 fingerprints in connection with the Marathon bombings, Graff said she reviewed a series of items from the investigation: a jar of nails, two rolls of tape, a soldering gun, an instruction manual, a pressure cooker lid, a transmitter from a remote control device and other items.

All bore the fingerprints of Tamerlan Tsarnaev, she said. None had the defendant’s fingerprints on them.

When Graff left the witness stand, defense attorney Timothy Watkins said the defense had no more witnesses to call. Attorneys tried to present photos, but prosecutors objected, prompting a sidebar conference with Judge George O’Toole.