Scent transfer unit

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A scent transfer unit is a vacuum device used to collect scent evidence from a crime scene or item of evidence.[1] The unit was invented by Bill Tolhurst (a former president of the National Police Bloodhound Association) while working for the Niagara County Sheriff's Department.[2] Several law enforcement agencies have bought scent transfer units.

The device works by sucking an odour from a desired object onto a sterile gauze pad placed over the air intake.[2] The resulting scent pads can either be given to a tracking dog, used in a 'scent lineup', or preserved in a freezer.[1] Tolhurst has claimed that evidence pads can be stored successfully in a frozen state for more than 11 years.[2]

Although the reliability of scent evidence in general has been called into question, certain experiments have demonstrated successful use of scent transfer units.[2][3]


  1. ^ a b Hess, Karen M. (2009). Criminal Investigation. Cengage Learning. p. 150. 
  2. ^ a b c d Sachs, Jessica Snyder (August 2003). "What the Cold Nose Knows". Popular Science: 20–25. 
  3. ^ Holden, Henry M. (2006). To Be a Crime Scene Investigator. Zenith Imprint. p. 108.