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The Survivability of Human Scent


Photograph of bloodhound sniffing for human scent evidenceWe thought you'd like to know that the new issue of Forensic Science Communications has just been published on our site. And it's full of fascinating stuff.

Take the article on the Survivability of Human Scent by Rex Stockham, Dennis Slavin, and William Kift. Rex is an examiner in our Explosives Unit; Dennis and Bill are bloodhound handlers for the South Pasadena PD and the Long Beach PD in California, respectively. These three worked together to develop a new approach to identify bombmakers and arsonists through human-scent evidence recovered from post-blast debris. Their feasibility study shows that human-scent evidence left by bomb handlers lasts...and can be used to identify them even after undergoing the extreme mechanical and thermal effects of an explosion or burning.

All you need is a good scent-recovery process and a team of highly trained bloodhounds and handlers.

A little background. Human-scent evidence is, by its very nature, fragile and easy to compromise. But just last year Jeff and Lisa Harvey demonstrated that technology can reduce its fragility by using Scent Transfer Units to transport the components of human scent onto sterile surgical pads. They then proved that trained bloodhounds could identify that scent and match it to a suspect, even days later and on contaminated trails through an urban environment.

This study takes those results one step further. Here's a simplified overview: four pipe bombs and two gas containers were handled by six test subjects for one to two minutes. The explosives were detonated or burned; the debris collected; and this evidence was processed by a Scent Transfer Unit onto sterile surgical pads, which were then aged for anywhere between two and 16 days. Each bloodhound handler was then arbitrarily given a scent pad to present to a dog.

Now the test. The bomb handlers and six innocent "decoys" were sent out onto trails in an urban public park. The bloodhounds were placed at the start of a trail, given a good sniff of a scent pad, and off they went--using their specially trained "yes" or "no" response to signify a match or no match.

The results? Overall, the dogs correctly identified the target person in 53 of the 80 bomb-debris experiments and 31 of the 40 arson-debris experiments with no false identifications. These are good results, supporting the general reliability of the procedure and indicating potential use in criminal investigations.

Interested in the details? Go straight to the Survivability of Human Scent. And while you're there, you may want to look at some other research articles too.

Links: The FBI Laboratory