New research shows that a bombmaker鈥檚 identity can be traced from DNA on fragments of an exploded device.
Kelly Esslinger at Michigan State University in East Lansing and Heather Spillane at the Michigan State Police Crime Laboratory in Northville set up an experiment to see whether DNA could be detected on exploded bomb fragments and matched to a suspect. They found traces of DNA on one in five bombs exploded under controlled conditions.
Ten subjects were asked to handle one metal and one PVC pipe bomb each. They were told to touch each component (the pipe, caps and fuse) for about 10 seconds. After storing the bombs for a month in sterile bags, the researchers exploded each in shallow holes covered with earth and a large rock. They collected fragments from inside the hole to avoid contamination from elsewhere.
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The researchers then applied a sensitive method of DNA fingerprinting which traces short tandem repeats (STRs). These short regions of DNA contain repeated elements of two to seven letters. Different people have different numbers of repeats at different sites, so the combination of enough sites constitutes a unique DNA fingerprint. Esslinger attempted to amplify 13 STRs from DNA on the bomb fragments.
Bomber fingered
Four of the 20 bombs had enough DNA on fragments to identify the 鈥榖omb-maker鈥�, the researchers told the Academy of Forensic Sciences annual conference in Chicago last week. From five others, the researchers could amplify some of the STRs, but not enough for a definite match.
Jonathan Whitaker, at the UK Forensic Science Service DNA unit in Wetherby says that he is using similar techniques in ongoing cases to identify bombing suspects. He says that extremely sensitive techniques such as STR are prompting a new approach to crime scenes. 鈥淲e can recreate in our heads exactly what a killer may have done,鈥� he says.
Esslinger describes the technique as a 鈥渓ong shot鈥�, and says she was most successful with the least powerful blasts. 鈥淭he less mangled, the better chance I had,鈥� she adds.
She says the technique would have been useful in hunting the 鈥榮miley face鈥� bomber who planted 18 pipe bombs in letterboxes in Illinois, Iowa, Nebraska, Texas and Colorado in May 2002, had police not caught up with him so quickly. 21 year old student Luke Helder was trying to draw a smiley face with the locations of his bombs. 鈥淗ad he still been at large, DNA is something they should have tried,鈥� Esslinger says.