Understanding Trace Evidence

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Trace evidence can be anything at a crime scene. If someone comes into contact with something at a scene, or even just goes to the scene and leaves, trace evidence can be left there. Edmond Locard is someone who we can thank a great deal when it comes to trace evidence. Edmond Locard was trained in both law and medicine. Back in 1910 Edmond Locard established a forensic lab located in Lyon, France.

Locard established a reputation when it came to forensic science in Europe, and some of the biggest things he was interested in was microscopic and trace evidence and especially dust. He believed that such trace evidence was crucial in linking people to places. So, he came up with Locards exchange principle. His principle evolved from his studies and writings, his principal is usually paraphrased as “every contact leaves a trace”. His belief is that contact between a person and another person or a person and a place leave’s some form of evidence.

A good example of trace evidence is when a car drives thru dirt or mud and goes to a different location leaving tire tracks of dirt and mud. The tires picked up the dirt and mud traveled to a different location from where it was picked up from and transferred to the other location. It seems quite simply yet there is so much detail when it comes to trace evidence and processing scenes for trace evidence. Knowing the proper ways to process and what to look for can make all the difference in a case.

Some of the methods of collecting trace evidence varies on the type of trace evidence and the location of the evidence. One of the more popular methods of collecting trace evidence would be using trace evidence tape. The technician would use tape and place it down on the location of where he or she believes there is evidence that needs to be collected and allow it to stick to the tape and lift it. Another method that goes along with the example I gave involving paint chips would be to collect the paint chips and place them into an evidence envelope and have it sent off for testing.

For evidence such as bodily fluids, or in the case below, semen, the technicians would use cotton swaps and swap the area of the possible bodily fluid they think it is and have that sent off. There is also test kits for semen and blood for technicians to use out in the field to give a positive reading of the area tested. This type of test cannot confirm that what the technician thinks it is, is exactly that, but gives them a baseline of the area in which to continue to swab. This is the same concept for patrol officers when testing what they believe to be some type of narcotic. The officers may have test kits for drugs such as methamphetamine, and cocaine. The test kit will change color to show a positive presence of that substance in which the test is for.

There are many different types of trace evidence, everything can be some form of trace evidence. There are things such as hair, soil or dirt, glass, and even paint chips. Trace evidence can be found by two cars bumping into each other transferring paint. Then the paint can be collected and compared to see where the paint came from and possibly a make or model of the vehicle. There are also two different kinds of transfer methods primary and secondary. An example of primary transfer would be soil imbedded in a suspect’s or even a victims shoes picked up at a location and released from those shoes at a different location.

The same if two cars hit each other in a hit and run type incident and paint from the victim’s car on the suspect’s vehicle falls off at a different location or found. The next type of transfer is secondary transfer. A good example of secondary transfer is when you decide to ride with one of your friends in their car, while in their car you have hair or fiber get onto your clothing. This could come from human, animal, or even fibers from an unknown source. But you pick those things up by being in a place and it gets onto your person. Another form of trace evidence that relates to the case I have chosen is bodily fluids.

There are things such as saliva that is produced by humans, someone can walk into a room and talk and leave their DNA due to saliva being in their mouth. Semen can also be left at scenes, such as sexual assaults or rapes. These types of evidence can be swabbed and collected and tested to see who they belong to by testing suspects or even victim’s DNA. One other form of trace evidence is gunshot residue. Gunshot residue can be left both on a person either victim or suspect and also on a surface. Technicians can test a suspect’s hands for gunshot residue and have the test sent off to confirm if it is or isn’t.

The case I have chosen to talk about is about a man who earned a name called “The Southside Strangler”. Timothy Spencer was known as a serial rapist and murderer who terrorized Richmond, Virginia back in 1987. Timothy Spencer at the time was pulling time in a halfway house in Richmond and was known as a burglar due to the breaking and entering’s he had committed. In 1987 there were 4 different women whom were raped and killed over a 11 week time period. Timothy Spencer’s first victim was Debbie Dudley Davis whom was murdered in her on home.

The next was a Dr. Susan Hellams, the youngest a Diane Cho, and Susan Tucker who was 44 years old. All the murders and rapes were similar however, investigators were thrown off when the last victim was raped and murdered in Arlington, Virginia instead of Richmond. Timothy Spencer was found out as the suspect by investigators by them testing semen found at each scene and testing Spencer’s DNA at a later date. One thing that really makes this case stand out compared to others is the fact that Timothy Spencer was the first person in America to be convicted of murder on DNA evidence. No one else in America had ever been charged with a crime and convicted off of DNA testing.

At the time DNA testing was something that was becoming new to everyone and luckily for these investigators it helped them with getting a rapist and murderer off the streets. Timothy Spencer was again convicted and charged with the crimes he had committed and was sentenced to death. On April 27, 1994 Timothy Spencer was executed, and just a few hours prior to this his defense attempted to appeal the case to retest the evidence however, the appeal was denied.

With knowing that trace evidence can be so many things, including the details in this case. It just shows that no matter what crime you commit there is always something that is either left or taken away from a scene that can be traced back to you. In Timothy Spencer’s case his actions caught up to him due to the ever-changing advances in technology. His DNA was there at the scene and due to his actions, he made a historical event out of his crimes that only betters the field of forensic science.


  1. Fuller, J. (n.d.). How Locard’s Exchange Principle Works. Retrieved from https://science.howstuffworks.com/locards-exchange-principle2.htm
  2. Holmberg, M. (2018, June 20). “The Southside Strangler:” Holmberg revisits one of the worst nightmares in RVA history. Retrieved from https://wtvr.com/2018/06/20/holmberg-revisits-one-of-the-worst-nightmares-in-rva-history/
  3. James, S., Nordby, J., & Bell, S. (Eds.). (2014). Forensic Science: An Introduction to Scientific and Investigative Techniques . Boca Raton, London, New York: Taylor & Francis Group.
  4. The New York Times. (1994, April 28). Murderer Put to Death In Virginia. Retrieved from https://www.nytimes.com/1994/04/28/us/murderer-put-to-death-in-virginia.html

Cite this paper

Understanding Trace Evidence. (2022, Jan 14). Retrieved from https://samploon.com/understanding-trace-evidence/

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