The testing of hemp and marijuana is one of the biggest challenges facing law enforcement officers in Tennessee.

Investigators with the Tennessee Bureau of Investigation (TBI) said the inability to tell the difference is impacting their resources.

Mike Lyttle, assistant director of the forensic services division, said it's an issue they are constantly dealing with.

"We've run into some confusion with law enforcement officers when they encounter plant material in the field and what it might actually be," Lyttle said. "Unfortunately it's fallen on the crime lab to help them tell the difference."

He said they both come from the same plant, Cannabis Sativa, but any substance under .3% THC or less is considered hemp.

"The only way to determine the difference is to do increased chemical testing to determine what it is," Lyttle said.

It's a change for TBI scientists. 

"Years ago we could simply put it under the microscope for a color test for properties unique to the plant, Cannabis Sativa and we were done," Lyttle said.

After thousands of submissions to the lab, TBI decided to implement a new three-step testing policy.

Threshold testing will determine if the submission is greater than 1% THC, while quantitative analysis allows agents to determine a percentage between 0.1% and 1%.

The average turnaround for a drug test is about 30 weeks for TBI's crime lab in Knoxville. The length of time is partially due to hemp, Lyttle said.

"We're on the path this year to receive almost 34,000 drug cases this year, that's a 50% increase without subsequent resources and staff," Lyttle said.

He said it would be helpful if officers were able to perform a color test in the field to determine if the sample was hemp or marijuana.

However, he said those tests run about $15 each.