Human Scent-Detection Device Under Fire After Cases Fail


A device used as a law enforcement tool to help bloodhounds detect human scents at crime scenes is under increasing fire after its use has led to the incarceration of at least five men whose cases were later dismissed, the Los Angeles Times reports. A Buena Park, Ca., man was freed from prison in October after serving almost a year for a carjacking and armed robbery he did not commit. He was released after a man jailed in Los Angeles County admitted to the crime, a confession supported by DNA evidence.

The device, known as a scent-transfer unit, or STU-100, was invented in the 1990s by engineer Larry Harris and a partner. Harris and others promote the $900 machine to law enforcement. Backers say the machine, which resembles a leaf blower, can collect human scent from an object as small as a bullet fragment and transfer it to a 5-by-9-inch gauze pad that is put to a bloodhound’s nose. The dog then theoretically follows the scent to the suspect. The machine allows the scent to be presented to the dog without compromising physical evidence. Experts debate whether bloodhounds can reliably identify a specific suspect by his scent under any conditions. Civilian dog handler Ted Hamm says he has used the device in most of the 2,000 cases he has worked. “I think it’s quackery,” said Prof. Larry Myers of Auburn University’s College of Veterinary Medicine and an expert defense witness in scent evidence cases. The dog handlers “have no idea how reliable the machine is.” In 2003, a California appellate court limited use of scent evidence in trials, saying the device and its operators must meet standards “generally accepted” as reliable by the scientific community – a benchmark that has not been achieved.


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