City, News

Tsarnaev trial jurors presented with digital evidence, expert testimony

Thursday began the 10th day of testimony in the trial of Dzhokhar Tsarnaev, the 21-year-old accused of planting two bombs at the finish line at the 2013 Boston Marathon that killed three and injured more than 260. He is pleading not guilty to all 30 federal counts for which he is being tried.

Jurors were presented with digital evidence and testimony Thursday about explosives in the trial of Boston Marathon bombing suspect Dzhokhar Tsarnaev at the John Joseph Moakley United States Courthouse. PHOTO BY ALEXANDRA WIMLEY/DAILY FREE PRESS STAFF
Jurors were presented with digital evidence and testimony Thursday about explosives in the trial of Boston Marathon bombing suspect Dzhokhar Tsarnaev at the John Joseph Moakley United States Courthouse. PHOTO BY ALEXANDRA WIMLEY/DAILY FREE PRESS STAFF

The day of expert testimony began with the continued testimony of Brian Corcoran, FBI special agent and bomb technician.

Corcoran explained the details of a pressure cooker bomb detonated on Laurel Street in Watertown, which had a blast radius of over one block. Photo and tangible evidence proved that this pressure cooker was the same brand as the two detonated on Boylston Street at the Marathon’s end, Corcoran said.

Corcoran described the technicality of the detonation, in an effort to confirm that there was a blast despite the lack of witnesses.

“We refer to a blast seat as somewhere where there was an object or device that shows evidence of an explosion,” Corcoran said.

Photo evidence showed a blast seat in the center of Laurel Street, and supporting evidence showed further evidence of a remote detonation by Tsarnaev.

The FBI investigation team found two bags within the block radius containing official school documents of the deceased Tamerlan Tsarnaev, the suspect’s brother; a thumb drive; a Samsung laptop; a transmitter; a detonation switch, which the prosecution referred to as a “dead-man’s switch” and Corcoran affirmed was “a last resort to initiate the device, should you be stopped”; and shrapnel.

The base of the pressure cooker was lodged into the door of a Honda Civic in a driveway near the blast seat, its lid on the opposite side of the street, found in a hockey goal. Both were mangled, with inner indentations indicating the pressure cooker was filled with BBs and metal pipe, as well as combustible powder, Corcoran said.

“Typically, when there is some type of fragmentation in an explosive device, you do get some sort of pitting, maybe from the screws or whatever may be inside,” he said.

Shrapnel littered the area around the blast, in nearby yards, siding of cars and lodged in the clapboard walls of houses, Corcoran said.

Three circular pieces of cardboard, each with burn marks and residue indicating an explosion, were found on site. Two were presented at the trial.

Corcoran testified that “the cardboard could be used as a barrier between different layers of the [blast] device,” because when elements of the explosive mix, it could harm the function of the device. Pieces of exploded metal pipe, also pitted and rusted, were found scattered in the area as far as the adjacent street, Dexter Street.

The second witness of the day was FBI Special Agent and Bomb Technician Phil Christiana, a 23-year veteran of the FBI. He visited the blast sites on Boylston Street on April 15, 2013 — the day of the Marathon bombing — and investigated the apartment of Tsarnaev’s close companions in New Bedford, New Hampshire, a few days later.

“We were sent there to assist the hostage rescue team as bomb technicians. After the hostage rescue team cleared the apartment for people, we were assigned to sweep the residence for potential hazards,” Christiana said.

After the house was cleared of its residents, and confirmed that it housed no hostages, Christiana collected anything that could provide evidence to Tsarnaev’s accusation. He seized a computer and three cell phones that were sent back to the FBI for imaging, processing and export, a process which was overseen by the third witness, Special Agent and computer forensics expert, Kevin Swindon.

Swindon explained the process in which the “digital media” from the seized items was copied and analyzed by the FBI, to be presented as viable, untainted evidence in court.

“Computer forensics has really evolved over the last couple of years as previous technology has become what it is today,” he said. “There is a process for what we do, including how we handle collection, how we process it and what we do when we image it. The primary focus is to acquire evidence in a forensically sound way to make it usable in legal proceedings. It can range from USB drives, to external hard drives, to servers and computers. There is an image phase and a processing phase. The imaging phase uses a piece of software to acquire, bit by bit, a forensic copy of that hard drive.”

The prosecution asked Swindon to affirm each piece of evidence as viable. Swindon said each image taken is cross referenced with the original and assigned a value, called an MD5 hash, that represents its accuracy.

He said the amount of digital media evidence collected was overwhelming.

“There were over 600 pieces of digital media collected. There were numerous different types,” he said.

Swindon took the stand once again after the lunch break. The entirety of the second half of the session consisted of references to a spreadsheet that accounted for all electronic devices collected for evidence.

Swindon began with several CD’s containing files and information stored on Tsarnaev’s Sony Vaio laptop. The laptop contained several files that were called into question, with titles such as “Jihad and the Effects of Intention Upon It.”

“We verified, based on the data sets available, that the data was there on the computer,” Swindon said.

The files also included an essay written by Tsarnaev entitled “The Predator War,” along with copies of the Al Qaeda-distributed periodical magazine “Inspire.” The particular copy mentioned by prosecution attorney, Aloke Chakravarty, included an article entitled “Make a bomb in the kitchen of your mom.”

“The name of that file was on a number of locations,” Swindon said.

Though a number of documents were not in English, Swindon said the FBI was able to make proper translations to understand the content.

“If the team encountered something that we needed translated, we have a full staff of linguistics fluent in numerous different languages that could translate,” he said.

Swindon also defined unallocated space, which was frequently questioned by Chakravarty, when files could not be properly opened. If the files were deleted or eliminated in some way, Chakravarty said, sometimes the entirety of the article cannot be salvaged. As a result, many files were reduced to JPEG images as evidence of their former existence.

“Carved Files are a hit or miss. If they can recover the file, the software does as much as it can to render the data it can get back, but you may not get the entire file back,” Swindon said.

Other examined electronic devices included iPods, a Samsung Finesse cellphone, two other CDs, two thumb drives, two iPhones and an external hard drive.

Further witness testimony is scheduled to resume Monday.

More Articles

Comments are closed.