Blank Image

What is the STU-100?

The Scent Transfer Unit (STU-100) was specifically designed for Forensic Specialists, Investigators, Evidence Response Teams, Identification Departments and Scent Dog Handlers. The Scent Transfer Unit allows law enforcement to collect evidence from any item without destroying fingerprints on the item, collect trace evidence at a crime scene without contamination, collect scent evidence from hard to access places not accessible to a search dog and gives law enforcement a scent pad to store in scent banks for future use on repeat offenders

The STU-100 was designed and built to assist law enforcement with the collection of scent and trace evidence. It provides a method of preserving evidence for extended periods of time because scent is evidence. The STU-100 requires common sense, good judgement, a sound working knowledge of scent and what it takes to protect it from contamination. Properly handled and operated, the STU-100 can produce unbelievable results.

The STU-100 has other uses as well.

Dog trainers and handlers can make scent pads from both narcotics and explosives to use in training. It is no longer a must that these items be checked out of evidence rooms for training. This is safer for everyone involved.

If you are training dogs for mold or termites or even bedbugs this can make your life a whole lot easier. The dogs also come in contact with a lot less mold spores over time.

Trainers if you have a dog in the field hours away that you want to check on, just mail five or six pads to the handler. Only you will know which one contains the odor. Have the handler set the pads out and work the dog and call you with the results. This is already being done at Forensic & Scientific Investigations in Vincent,Al. You can contact Master Trainer David Latimer at for details.

At Tolhurst Big "T" Enterprises we are always trying to get the handlers and trainers involved in research. This enables them to think outside the box which creates better trainers, handlers and dogs.

Through the use of the STU-100 we are now able to train dogs to take a given scent from a pad and having the dog match it to one of a group of pads that are placed out in a room. You can more readily connect crimes that are related by using the scent evidence.

In theory we could have a serial killer active in multiple states connected to all of the crimes through scent. immediately as an investigator you would start looking for people who have jobs that require travel to these states. We are only limited by our ingenuity.

STU 100

All of these things are being done already in places like the Netherlands where their dog training is legendary. The STU-100 is there as well.

Trainers feel free to call us or email us if you want more information or a demonstration.


The suspect at any crime scene leaves behind human scent evidence. Every person in the world has his or her own personal scent. Each person’s scent is made up of his or her own skin cells, bacteria, etc. and your personal scent is as individual as your fingerprints.

By using the STU-100 (Scent Transfer Unit), human scent evidence is vacuumed into a sterile gauze pad, double bagged and heat-sealed in a Kapac bag. Sealed scent pads can be stored in a scent bank and can be used at a later date, when a suspect is developed.

Scent evidence can be collected, preserved and then used long after the crime scene has been abandoned.

Studies are under way to compare human scent evidence (HSE) with DNA, using the human scent retained in the STU-100 pads. The STU-100 has been operational since 1996 and is court proven.

There are a large number of STU-100’s in service in the United States, Australia, Japan, United Kingdom and the Netherlands. Units are currently in service with the FBI.

In the fall of 1999, members of Bloodhound Handlers Coalition (BHC) began researching recovery of human scent from explosive’s evidence at a trailing seminar in Beloit, Kansas.

History of the STU100

"The Scent Machine" In the late 80'S I tried using a vacuum process to collect the scent into a sterile gauze pad that I could move around and better yet, I could collect the scent and keep it for long periods of time. A number of 110 models were tested. I called them "Scent Transfer Machines" however as with most first inventions they were big, heavy, cumbersome and while they did the job well they were difficult to handle.

With the help of his partner, Larry Harris, Bill was able to reduce the size of the scent machine and take it from a 110 volt system to a 12volt system that is portable and contains its own power supply.

A bomb technician set up a pipe bomb test. “Suspects” handled the bombs and placed them at the “crime scene” – an abandoned car in a field outside Beloit – then the “suspects” left the scene.

Once the bombs exploded, the car caught fire and was extinguished with water. After the scene was cleared, the recovery of bomb fragments began. Human scent was collected from the fragments, using the STU-100. The bloodhounds trailed from the bomb fragment STU-100 scent pads and identified the “suspects” who handled the bombs.

In the years since the Beloit seminar, members of the BHC have set up numerous research tests ranging from car fires to large-scale vehicle bombs. One of the most recent tests, in March 2005 involved a 2000-pound bomb, which was used to explode an old military crash truck. Despite devastating damage to the crash truck six (6) bloodhounds were able to successfully trail and identify the suspect in a series of blind, split trails using the STU-100 to collect human scent from assorted bomb debris.

The word of BHC success in the field of arson and bomb evidence began to spread. Personnel with the FBI Explosives Unit contacted BHC to do a series of studies. After the various devices were detonated or burned, human scent was collected using the STU-100. The end results conclusively showed the FBI that well-trained bloodhounds could successfully take scent from arson and bomb evidence, trail to and identify the perpetrator of the crime.

Since the FBI study in 2001 involvement in human scent evidence collection in arson and explosive type cases has increased dramatically on a national level.