Cannabis Expert Witness: 6 Reasons You Need to Retain One

Joseph O'Neill

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— Updated on February 12, 2021

Cannabis Expert Witness: 6 Reasons You Need to Retain One

When defending a client in a case involving marijuana – whether the issue is DUI, possession, or exploiting the medical marijuana system, hiring a cannabis expert witness should be one of the first things that you do. From countering the prosecution’s expertise, to evaluating drug testing methods and police procedures, to educating the jury on the current state of scientific discourse surrounding pot, a cannabis expert witness can make a case long before it even goes to trial. We’ve spoken with leading criminal defense attorneys, cannabis expert witnesses, and law enforcement officials to get their perspective on the different ways attorneys can utilize these important experts on their cases.

1) Put The Opposition on Notice

When dealing with drug offenses – an area in which most defendants choose to make a plea bargain – retaining a defense expert shows the prosecution that you and your client intend to vigorously fight the charges. “Retaining a marijuana expert effectively puts the prosecution on notice,” says Paul Armentano, Deputy Director of NORML and cannabis expert witness. In a document released by NORML, “Cross Examination of Police Expert in Cannabis Cultivation and Possession for Sale Cases,” attorney William Panzner places a high level of confidence in retaining a defense expert. Saying that if defense attorneys can retain a defense expert to “do it. There is no substitute.”

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If an expert is retained early enough, a trial can be avoided altogether. “Usually, if the defense hires an expert, the case can be beaten at the motion and deposition level before it gets to trial,” Armentano says. Christopher Corso, an Arizona-based criminal defense attorney, agrees “As with any new battleground in the legal field, the quality of your case can many times rely on the quality of the experts you choose to support your case.”. Bringing a cannabis expert witness onboard can show the prosecutor that your case will not be an easy one.

2) Counter the State’s Expertise

When defending a marijuana charge, the state will often produce their own cannabis expert witnesses to evaluate the evidence seized by the arresting officers, the behavior observed by the arresting officer, or the amount of marijuana that could conceivably be used for either personal or medicinal use. Often, these experts will be experienced law enforcement officers who are indeed experts in their field. However, they may lack the appropriate qualifications and reliance on scientific data to produce sustainable expert opinions on marijuana.

“Often, the law enforcement officers that are called by the prosecution will be on the wrong side of the science,” says Armentano. Law enforcement officers will often be trained as “Drug Identification Experts” indicating that they have taken a course administered by the National Highway Traffic Safety Administration (NHTSA), where they learn how to identify behaviors and physical symptoms consistent with the use of particular drugs. While the program claims scientific foundations, there are some aspects of its identification protocol that experts claim are not reliable. Armentano says, “Often, police officers will claim that the drivers had a green or brown film on their tongue, or that they witnessed eye tremors. They’re told to look for these signs in their training, but neither of these symptoms appears in the medical or scientific literature surrounding marijuana intoxication.”

“The DRE program is a big money maker,” said Dr. Jordan Tishler, a Massachusetts-based internal medicine physician and medical marijuana advocate “DREs have some literature to support their expertise, but also significant literature showing variability.  A large part of the problem stems from the fact that the tests they use, namely the standardized Field Sobriety Test, have only been validated for alcohol, not other substances.  Yet they are applied to all cases.”

Christopher Corso agrees “DREs aren’t nearly as qualified as doctors to speak on impairment, and aren’t highly educated on the medical aspect of whether the driver was impaired. They have undergone training and courses to “recognize” impairment based on their previous experiences as well as a person’s behavior and actions.”

“That’s why highly qualified drug experts are so crucial if your client is ultimately charged,” Corso says, “For us, science trumps what a DRE might see on the side of the road.”

3) Speak to Acceptable Medical Use

With the rapid emergence of medical marijuana to 23 states as well as Washington D.C. issues of marijuana for personal, medical use and illegal distribution have begun to emerge. What is in question in these cases is not usually whether the individual was under the influence of marijuana at the time, but whether the marijuana possessed by an individual could conceivably be used for illegal sale to non-medical users. Often, experts can be used to inform juries (who may be totally ignorant of medical marijuana treatments) about what is acceptable for medical use, such as in the case below:

Background: Defendant was convicted in the Superior Court, San Diego County, No. SCD244120, Peter C. Deddeh and Albert T. Harutunian III, JJ., of marijuana possession (1.26 pounds, above the 8 oz. limit for personal medical use) and cultivation. The defense appealed claiming that the law permits qualified medical marijuana patients to join together to cultivate marijuana to meet their medical needs.

Expert:Defendant testified on his own behalf and called two expert witnesses (patient advocate William Britt and naturopathic doctor Michelle Sexton) to support his claim that he possessed the marijuana solely for medical purposes. Defense expert Britt testified that patients frequently use scales (like the one discovered in the defendant’s posession) for portion control, and marijuana can last up to two years if kept in a cool, dark place, and even after two years it is still usable.

He stated that the 1.26 pounds of processed marijuana in the plastic bags was entirely usable. He estimated there was about three to four pounds of usable bud in the hanging stems; about 10 grams of usable bud in the tub; and about one-half pound to one pound of leaves in the tub that could be used for baking. Relevant to the outdoor plants, Britt explained that the amount of anticipated yield depends on such factors as plant size and the size of the plant’s canopy. He opined on the seven plants found outdoors and attributed to defendant would yield a total of about three and one-half pounds of bud and the two smaller plants (belonging to Jones personally) would yield about two to three ounces.

Britt testified that because of the growing seasons most people can only harvest marijuana once per year. Thus it would be reasonable for a patient to cultivate enough to last for one or two years. Defense expert Dr. Sexton testified that marijuana is a “pretty stable compound” under ideal storage conditions, although it does degrade over time to some extent; for example, a plant might degrade from 10 percent to 8 percent THC content after the passage of a year.

She testified a joint typically contains about one gram of marijuana, and the effects last about three to four hours. She stated doctors do not typically recommend a specific dosage of marijuana. This is because there is a high level of variability in patient tolerance levels and plant potency. Patients are normally told to use the amount that gives them pain relief. Although recognizing this was an “inexact science,” Dr. Sexton estimated defendant could reasonably use about eight grams a day of marijuana to control his chronic pain. For example, he could use about one gram every three hours, including during the night. Or he could use a higher dosage during the night when pain tends to worsen, and a lower dosage during the day.

Medical cannabis can also have implications in insurance scenarios. As Tatiana Kadetskaya, a Philadelphia based life insurance attorney, says “More and more life insurance claims are denied now due to marijuana. At least twice a month, we get a call from a beneficiary whose claim has been denied due to the insured’s marijuana use.”. Still, as Kadetskaya notes, insurance companies will often allow for the use of medical marijuana, as long as the patient discloses their prescription. “Usually, claims are paid if people are prescribed marijuana and take it within the limits prescribed by their physician. However, if the insured took marijuana for medical purposes but failed to disclose it on the application, the claim may be denied.”. According to Kadetskaya, insurance companies will usually rely on toxicology experts to determine whether the deceased had been using marijuana.

4) Communicate with the Jury

According to attorney Aaron Pelley, cannabis expert witnesses with experience in working with medical marijuana in a clinical capacity can be vital in explaining the palliative effects of the drug to juries “What a good medical expert can really help with in DUI cases is the fact that users of medical marijuana are not necessarily in an “altered state” when they’re under the influence of the drug; they’re using the drug as medicine to get from an altered state to a healthy baseline.”

Dr. Tishler says marijuana “…has many therapeutic uses.  It’s great for pain control (acute or chronic), for depression and anxiety, muscle spasms, nausea and vomiting, anorexia.  It’s also been shown to modulate inflammatory response in Crohn’s and Rheumatoid arthritis.”. Hearing the medical benefits of marijuana enumerated, or hearing an established expert outline the science behind marijuana intoxication, can help the jury understand a defendant’s use of the drug and prevent them from dismissing the user as an “addict” or “junkie”. In Pelley’s experience, experts can play a major role in informing a jury’s decision, “Juries are generally receptive to expert opinions. I’ve had jurors come up to me after trial and tell me how much the expert’s testimony affected their decision.”

5) Assess Plant Yields and Paraphernalia

In a 2002 Supreme Court of California case People v. Mower 28 Cal.4th 457, a defendant accused of the illegal cultivation of marijuana found himself on the wrong end of a prosecution expert, who claimed that the 31 plants he had been discovered with would yield anywhere between 31-62 pounds of usable marijuana buds. To counter this assessment, the defense brought in an expert of their own. They testified, based on agricultural and other assessments and projections, that the plants probably would yield a harvest of 4.35 pounds. The supreme court reversed the guilty verdict of the lower court largely based on this evidence.

Will Panzner says “You should always personally inspect the cannabis (in a criminal possession case). If you can, bring a defense cannabis expert witness with you. Don’t accept any representations made by the police. Inspect and weigh the cannabis yourself. You will usually find that the police have overstated the amounts, often ludicrously so. If you are dealing with plants, consider seeking a court order to have your expert process and manicure a plant or plants to more accurately determine the yield.”

6) Assist in DUI Cases

DUI cases in which marijuana is involved are complex. They are an area in particular where experts can be used to significant effect. According to Christopher Corso “If a DUI is involved, the situation becomes much more complex, and the support of an experienced cannabis expert witness is crucial. Unlike alcohol, marijuana traces, or metabolites, remain in the system for longer periods of time. An expert is needed to discuss how metabolites affect the body and whether these trace amounts of the drug resulted in impairment.”

In DUI cases, prosecutors may also rely on the testimony of toxicologists to establish marijuana intoxication on the part of the defendant. This approach, however, may be fundamentally flawed, due to the enduring presence of THC in the body after initial intoxication. “Previously, the intent of the test was to catch all users, because use of Cannabis was illegal” says Dr. Tishler “Now that it is legal (medically or otherwise), the question has to change. Now we need to know who is presently intoxicated (not who has ever used).  As such the current test measures the wrong agent.  The current test is for COOH-THC which is…a long lasting cannabinoid.  Tests for plain old THC are rare, but usually only positive for 4-8 hours.  This is still too long and other metabolites need to be identified that dissipate around the 4-hour mark (when intoxication from inhaled MJ typically wears off).”

As for the safety of using medical or recreational marijuana behind the wheel, the jury is out. Dr. Tishler says “This is a touchy subject. For liability reasons, one can only state that driving under the influence (whether a patient or recreational user) is illegal and unsafe. That said, there is growing literature that shows “experienced” users have less impairment than others, and in some cases may even be deemed safe. On the other hand, we know that all substance users (meaning alcohol and Cannabis) overestimate their abilities.”

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