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Improvised explosive devices (IED) like pipe bombs are the weapon for choice for some terrorists and lone-wolf attackers who want to wreak havoc while keeping themselves out of harm’s way. The attacker gets a running start to escape even before the smoke clears, and the high heat of a blast can degrade the already-low amount of DNA the careful bomb maker leaves behind on the device. 

But new DNA sequencing technologies could be opening up new avenues of identifying bombers, according to a recent study in the journal Forensic Science International: Genetics.

The Sam Houston State University scientists looked at three different methods of analyzing touch DNA traces on shrapnel: STR analysis, insertion/null (INNUL) markers, and SNPs via the latest “next-generation” sequencing.

Ten pipe bombs loaded with Tannerite were exploded by the scientists. The devices had shrapnel touched with trace blood from people of three different races – to mimic the wounds of victims. But the wires that fused the pipe bombs together were touched with a miniscule of DNA cells from the “bomber.”

The 10 bombs produced 83 fragments. Forty-four of those had quantifiable amounts of DNA. The nine wire samples remaining produced seven full STR profiles.

The INNUL tool used was the InnoTyper 21 Kit. The “next-gen” work was done with the HID-Ion Ampliseq hardware, using Ion Chef and Ion PGM sequencing capabilities.

The INNUL and the “next-gen” sequencing showed promise in filling in gaps in the DNA degraded in the blast, they conclude. Of the 25 INNUL samples, nine resulted in complete genetic profiles, and another contained between 80 and 99 percent of the alleles.

They found the “next-gen,” or massively parallel sequencing (MPS), was fairly accurate in identifying ancestry from the touch DNA left behind after the blast. But it still requires refinement to work.

“MPS technologies need additional optimization for analyzing extremely challenging samples, particularly with LT-DNA samples,” they write. “NSP analysis via MPS offers great potential in identifying samples with low levels of DNA and moderate degree of degradation.”

Lead author Esiri Tasker, a Sam Houston PhD student, said in a school statement that the latest advances could compliment a toolbox which has not been equipped traditionally to pull DNA from explosive fragments.

“While forensic DNA technology has made several advancement since the 1980s, the ability to produce high-quality DNA profiles from IEDs can still be quite difficult,” Tasker said. “Issues such as high heat or low amounts of DNA can cause a DNA profile to be incomplete, or fail to produce a profile at all. Without the full picture, it is harder to identify suspects with DNA.”

Indeed, Bombs have shown to be a particular challenge to forensic DNA specialists. For instance, the chaos of the life-saving efforts in the wake of the Boston Marathon attack in 2013 forced police and hospital personnel to improvise their response in the aftermath of the deadly attack. Questions about whose DNA – and whether the dead attacker’s wife was involved in making the pressure-cooker bombs – persisted for months as detectives continued to analyze the forensic traces left behind.

Bobby LaRue, one of the Sam Houston State researchers on the paper, said the team planned to seek funding and to pursue further genetic markers that could survive high-explosive blasts.

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