The Tennessee Bureau of Investigation, which operates three branches of crime labs located in Nashville, Knoxville, and Memphis, completed over 70,000 lab tests during the 2018-2019 fiscal year.

The facility located in Nashville is the largest and receives the bulk of the cases from around the state. The facilities include a forensic chemistry lab, a toxicology lab, a forensic biology lab, a CODIS lab, a firearms identification lab, a microanalysis lab, a latent prints lab, a breath alcohol calibration lab, an evidence receiving lab and a crime science response lab.

Glen Jay Glenn, a special agent forensic scientist and composite artist, assists with investigations by drawing perpetrators that victims describe.

"I'll gather information just based on what they can recall. I get them to open up and feel comfortable," Glenn said. "Sometimes an individual may be kind of withdrawn if the trauma is great. For some, it's a way to start expressing and start venting about the event that happened, while honing in on the individual. I try to take this information and put it on paper."


The forensic chemistry unit provides testing of drugs seized in violation of drug laws. The tests conducted in the unit can help identify the type of drug as well as the weight and potency. Over 10,000 drug submissions the forensic chemistry unit receives each year are THC related, and about 500 of those are vape pens, gummies, brownies and other, non-plant based, THC. THC is the psychoactive component of marijuana.

The unit has several different tests it can run to determine if a plant is hemp or marijuana. Tennessee state law says that anything with more than 0.3% THC content is defined as marijuana.

"It's the same plant, it's the same species. It looks the same, feels the same and reacts the same to a lot of field tests," said Mike Lyttle, a TBI assistant director. "This has been one of the greatest challenges in forensic science over the last couple of years. How do you tell the difference between marijuana and hemp?"

The color test is a quantitative test that helps these scientists differentiate by using the ratio of CBD to THC in the plant. The test takes only minutes to perform. The scientist uses test tubes and a sample of the plant. If it shows up as blue, it means the THC levels are higher than the CBD levels, but if it shows up as pink, it means the opposite.

TBI has a number of other state-of-the-art facilities to assist in criminal cases. TBI is equipped with a full gun range, where employees can try out different weapons to help them determine what may have been used during a crime. They also have a full latent prints lab, where they have several different tools to match fingerprints, tire prints and shoe prints that may have been left at the scene of a crime.

"We appreciate the working relationship we have with the Tennessee Bureau of Investigation," said Lt. Scott Moore of the Wilson County Sheriff's Office. "They always present themselves with professionalism and integrity while conducting very thorough investigations within our county."

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