The secrets of bomb forensics

At the New Yorker, Paige Williams visits forensic chemist Adam B. Hall to talk about the surprising things you can learn about bombs and their makers by looking at the effects they produce — from the type and color of the smoke, to the smell that lingers in the air, to what the "boom" sounds like. I'd take Hall's speculation about the Boston Marathon bombings with a grain of salt (he's making his judgements from low-grade video and isn't part of the investigation), but the process he describes is absolutely fascinating.


  1. I think the mix of materials in the shrapnel is interesting. It seemed to be a mix of metals from one bomb and just or mostly nails from the other. I have cans in my garage containing junk metal. mainly nails, screws, brackets and such like. It sounds like the bombers went to a source of junk like that for one of the bombs but put mostly nails into the other. I reckon a foreign bomber would have bought nails for the purpose, and there would be little junk metal.

  2. Forensics is a rich field, and one that a regular person can practice all the time. It’s similar to reverse engineering, gathering clues from the object to piece together its original design.

    I once was working with a new programmable logic part which had some odd restrictions on use of internal logic elements. I deduced from these restrictions what the internal architecture of the part was. When I talked to the architect of the part later and revealed my understanding of the architecture, he said, “that’s a secret! How did you know that?” I explained that it was right there in the data sheet, that this input and that one couldn’t be used at the same time, therefore there was a selector to choose only one of them.

  3. The prof said “Let’s say you’re at a fireworks demonstration and you see the explosion
    and then hear the boom. That means the speed of light is faster than the
    speed of sound.”

    Um, yeah. Always the case. Never known sound to travel at or faster than light.

  4. Interesting point being: AFAIR authorities do not speak of ‘high explosives’, but of gunpowder or suchlike.  Let’s wait and see.

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