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Hemp or Cannabis? Texas Forensic Lab Adopts New Method to Tell the Difference

By Alexander Beadle

Published: Sep 16, 2020   
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The Houston Forensic Science Center (HFSC) in Texas has adopted a new testing method for differentiating cannabis from legal hemp, making it possible to once again provide state courts with the information needed to proceed with marijuana enforcement cases.

Speaking to Analytical Cannabis, the scientists behind the new method explain how it is able to determine whether the Δ9-THC present in tested material is above or below one percent by weight, and thus whether it is either legal hemp or illicit cannabis.

A better solution for law enforcement

After the 2018 Farm Bill legalized hemp production at the federal level, and the Texas Legislature subsequently adopted House Bill 1325, the state officially defined legal hemp material as cannabis containing less than 0.3 percent Δ9-THC.

But this language presented a problem for law enforcement. In light of the new legislation, some district attorneys requested that law enforcement agencies involved in cannabis prosecution cases provide lab reports positively identifying evidence as cannabis. But state crime laboratories did not have the capabilities to measure such levels of Δ9-THC in cannabis products. The expense associated with sending unknown cannabis material to private laboratories often meant this was only done for the largest felony cases.

With this new method in place at HFSC, Houston prosecutors will now be able to use public laboratory test results in cases where plant material has been seized and can be tested. The method is somewhat limited in scope as it is not effective in analyzing waxes, edibles, or other non-plant materials, but the HFSC believes that the method will be able to address the vast majority of cases presented.

Choosing an analysis method

Previously, the international lab standards organization AOAC International has approved an analytical method for measuring Δ9-THC content in hemp. This method relies on using liquid chromatography-diode array detection (LC-DAD), which involves equipment that is not currently standard in state labs such as the HFSC.

The challenge for analysts here, explains HFSC CEO and president Dr Peter Stout, was to produce a method that can fulfill the needs of law enforcement without requiring significant investment in new equipment or pursuing new accreditation.

“All [forensics labs] are accredited for qualitative analysis. Very, very few labs have drug quantitation as part of their scope of accreditation, so [we were] trying to devise something that we could fit into the existing accreditation,” Stout told Analytical Cannabis. “Also, having no foggy clue where this is going to go in the next legislative session, the twists and turns of who's actually going to enforce what, it makes it very difficult to justify adding expensive new equipment.”

“So, trying to devise a method using equipment that already we have in existence, we went with gas chromatography mass spectrometry, GCMS, because that's what we use largely qualitatively with most of the drug analyses.”

Taking inspiration from a semi-quantitative procedure established by the US Drug Enforcement Administration’s Analysis of Drugs Manual, the HFSC adopted the concept of using a one percent semi-quantitative over-or-under decision point for determining whether a material sample should be classified as cannabis or hemp.

“We went with one percent because we're trying to avoid issues of analytical variants around that point three [percent]. Basically, if you think about the logic of it, everything's devised in there to be as lenient towards the defendant, so we know we are not polarizing the material,” Stout explained.

“You've got a material that departs the farm with appropriate agricultural testing, that say has Δ9-THC content in the fiber of 0.29 percent. Things happen, material's seized by law enforcement, material comes to me in the laboratory,” Stout said.

“Because there is no actual definition of what 'dry' is [in dry weight], we're all left to our own devices. I can easily say I'm going to stuff [the material] in the oven and cook it at 50°C for two weeks. It'll be good and dry by then; I probably will have reduced the weight by half and I will have decarboxylated just about all the THCA to THC. That could easily mean that material now exceeds that one percent level, and in the criminal setting that material is now marijuana. That doesn't work.”

The HFSC lab tests the material they receive without any additional drying steps. Starting out with a macroscopic inspection of the material to identify any cystolithic hairs and a simple Duquenois-Levine color test to confirm the presence of cannabinoids, the analysts then follow with the new GCMS-based testing method, using deuterated Δ9-THC as an internal standard to identify and measure the Δ9-THC content in a given sample.

The future of forensic testing

HFSC is aware that this new method is limited in scope by virtue of using a one percent over-or-under decision point in its analysis. As a result, stakeholders will be asked to acknowledge these limitations in an end-user agreement, and HFSC will also note this on all final reports. But the method does represent a much more practical cannabis testing solution for law enforcement agencies in Houston, and one which has been developed effectively without external funding.

“When this legislation passed, in addition to all of the other problems that it created, [the state legislature] didn't provide any funding for anybody,” Ramit Plushnick-Masti, director of communications and public information officer at HFSC, told Analytical Cannabis. “They said this is going to make money. So, the crime labs have received no money to actually be able to assist with the enforcement side of things for what remains a controlled substance.”

“So, Texas' legislature, which meets every two years for six months, they will start their new session in January 2021. The hope would be that this would come up again, and that they would actually this time provide some resources. If they want to continue enforcing this law, then they need to step up and provide some resources.”


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