Forensic Science of Marijuana and Rule 702

The beginning and end of the Chemical Defense Revolution: How far can we stretch the Daubert decision? “Wacky Weed” v. Daubert

The Chemical Defense Revolution of 1972

This forensic chemistry revolution was made famous by Bob Shapiro and James Shellow. It was they that insisted forensic chemists conduct accurate and comprehensive analyses of which then brought forth an entire series of education to be learned from the laboratories to the courtroom attorneys. Laboratories then became subject to having to perform rigorous and responsible analysis.

PART 1: Death of a Revolution: The Chemical Defense Death

In 2007 the revolution takes a prompt death when US District Court Judge William Alsup declared that the combination botanical exam/Duquenois-Levine test for marijuana were valid, confirmatory tests of which had never rendered false positives. Ironically, it was in 1972, that Thornton/Nakamura defined this analytical protocol for determining the presence of marijuana, requiring microscopic analysis of the botanical features as well as the Duquenois-Levine test, a chemical “spot” test used in our crime laboratories and field testing today. Nakamura noted that Cannabis sativa is classified as follows:

Division: Spermatophyta (seed plants)
Class: Angiospermae (flowering plants)
Subclass: Dicotyledons (dicots) 31,874 species
Order: Urticales (elms, mulberries, nettles, and hemps) 1,753 species
Family: Cannabinaceae (hops and marijuana) 3 species
Genus: Cannabis
Species: Sativa
Nakaurma, G. R., 1969, Forensic Aspects of Cystolith Hairs of Cannabis and other Plants, Drug Abuse Control.

Therefore we are looking at defining a plant that is seed bearing, has flowers, is a dicot, and has some or all of the features of elms, nettles, mulberries, and hemps. Since most marijuana examine by forensic laboratories is crushed and may no longer retain the gross botanical characteristics, Nakamura notes that the presence of Cystolith hairs on the leaf fragments has been used as the principle criterion for morphological identification 2. Nakamura’s 1969 paper presented a protocol for analysis of seized marijuana samples as follows:

• A leaf specimen (100 mg sample) was macerated in 25 ml petroleum ether, filtered into a beaker, evaporated to dryness without heating, and tested by the Duquenois-Levine (D-L) test as described by Butler.
• For morphological examination, leaf specimens were studied under stereoscopic binoculars, 10 to 50X, and a simple compound microscope, 50-100X; 50-100: the subject was illuminated with narrowly directed reflected light of “Flexlight” unit (Iota-Cam Corp., 28 Teal Rd., Wakefield, Mass.) which is capable of producing 3,000-11,000 candle powers.
• Photomacrography was conducted through a 16mm Zeiss lens mounted on a 35mm Leica by aid of Visoflex reflex and bellows attachments. Kodak Panatomic film was used. Unless otherwise indicated, all prints were enlarged to a final 60X magnification for all specimens to provide size comparison.2,4.

Figure 1. Photomicrograph of a cross section of a marijuana leaf. 5
Figure 2. Cross section of a marijuana leaf. 6

A cross section of the marijuana leaf reveals the presence of bear-claw shaped hairs on the top surface of the leaf as well as clothing hairs on the bottom of the leaf. The aim of the forensic analyst is to observe these features through observations, through microscopic analysis of a suspected leaf, or through simply microscopically observing the top and bottom of the leaf.3

Only after a studied examination, under high magnification, can the Cystolith hairs of marihuana be tentatively identified. Microscopic identification of marihuana, therefore depends not only on the presence of Cystolith hairs but on its association with the longer clothing, or nonglandular hairs, on the other side of the leaf, and if present, the fruits and their hulls, the glandular hairs, and the flowering tops as set forth in US Treasury Department Manual. The D-L test should be used in confirmation.5

On this note, Nakamura’s dependence not only the cystolithic hairs, but also, if present, the fruits, hulls, glandular hairs, and flowering tops has most likely left an analyst with a protocol without clear parameters. Is there a defined minimum standard or protocol for determining identification for marijuana?

Nakamura’s paper has been critically reviewed by many regarding the number of plants studied that have Cystolith hairs. Robert F. Thorne reports in (2002) “How Many Species of Seed Plants Are There?” that there are 199,350 known species of Dicotyledons. Should we assume that law enforcement officers and their specialized training, experience, and education include botany and taxonomic features of plants and attest to what they are seeing is indeed marijuana to the exclusion of all other plant material? By the same token, is it probable that forensic lab examiners, after having detected the presence of bear-claw hairs on leaf surfaces and then subjecting the material to the D-L test are uniquely identified to be marijuana to the exclusion of all other plant material? According to Thorne 199,350 other plants exist that possibly share similar characteristics of marijuana.

At more than 70 years later, the D-L test has yet to be validated despite being involved in the arrests, prosecutions, and convictions of millions of individuals. The handfuls of forensic studies done to demonstrate the accuracy and reliability of the D-L test and justify its use in cases are themselves invalid and have obvious flaws. For instance, typical of forensic science articles on drug tests was a seemingly authoritative 2000 study funded by National Institute of Standards and Technology (NIST) and co-authored by Alim A. Fatah of the Office of Law Enforcement at NIST which claimed to have validated the D-L test. Indeed, the title of the article published in Forensic Science International was “Validation of twelve chemical spot tests for the detection of drugs of abuse.” To validate a drug test means to demonstrate that it is specific, i.e., the test identifies that specific drug to the exclusion of all other chemicals. According to the authors themselves, they did not validate these 12 tests because they found they were non specific, i.e., rendered false positives. “A positive CST (color spot test),” they wrote, “may indicate a specific drug or class of drugs is in the sample, but the tests are not always specific for a single drug or [class]” The term “not always specific” — as well as “relatively specific” which was also used by the authors — is unscientific, illogical, deceptive, and indicates unreliability. It should be noted also that there are literally millions of compounds that were not checked to determine whether they rendered false positives with the D-L test. In fact the authors ignored scientific articles which have reported more than a hundred substances which rendered false positives with the D-L test.9

Even if they had somehow found the tests to be specific, it would have been meaningless due to the fact that they admitted the D-L test is subjective: “[A]ctual color [may] vary depending on [the] color discrimination of the analyst.” In other words, an analyst’s or police officer’s vision (including that of the authors) could cause a false positive or even a false negative. Without resolving this impediment to accuracy and objectivity, the test should not be concluded as anything less than a screening test procedure. People are arrested and jailed on the basis of this subjective test. By definition, subjective means unreliable. A common definition of “subjective” found in any English dictionary: “Existing only within the experiencer’s mind and incapable of external verification” leads us to realize that the results of the D-L test are inadmissible as evidence under Daubert. The D-L test adversely affects the life, liberty, and pursuit of happiness of millions of individuals. This study is part of this adversity as it is cited by drug analysts, prosecutors, and judges in justifying its use and admitting its results as evidence. It was recently so cited in the USA v Diaz case in San Francisco, a drug case involving the death penalty. Indeed, citing this and other invalid studies, U.S. District Judge William Alsup declared: "Despite the many hundreds of thousands of drug convictions in the criminal justice system in America, there has not been a single documented false-positive identification of marijuana or cocaine when the methods used by the SFPD Crime Lab (which include the D-L test) are applied by trained, competent analysts." A few months before Alsup’s declaration, the U.S. District Court for the Southern District of New York decreed that: “False positives — that is, inaccurate incriminating test results — are endemic to much of what passes as forensic science.” Even a manual that accompanies the D-L field kit states that: “There is no existing chemical reagent system, adaptable to field use, that will completely eliminate the occurrence of an occasional invalid test result.” (Kelly 2008)11

The best known D-L “validation” study was published in 1972 by John Thornton and George Nakamura. It instantly became the gold standard and protocol across the country for marijuana identification and still is. On the front page of this article it states that the D-L test is a “confirmation” test “of marijuana.” By definition, confirmatory tests are valid and reliable; prove the presence of a drug beyond a reasonable doubt; and are specific, i.e., identify the drug to the exclusion of all other drugs and do not render false positives. They are also selective, i.e., do not render false negatives. As Jay Siegel has written: “A confirmatory test is one that has the capability of identifying a drug after it has been presumptively identified by another technique, thus eliminating all other substances from consideration. Since it is not possible for drug chemists personally to test all the millions of known substances against an unknown in a particular case to make sure the test is specific, a confirmatory test must be theoretically specific; that is the analyst can predict that it would not respond in the same manner to other untested substances.”10

In 1975, Marc Kurzman and his colleague questioned the Nakamura/Thornton validation study noting that the sample of plants checked for cystolithic hairs and tested with the D-L test was inadequate. Where Nakamura and Thornton described a population of 31,874 dicotyledonous plants that needed to be excluded with the protocol they were validating, Kurzman’s references described over 195,000. Nakamura and Thornton also reported two non-marijuana substances found to render false positives with the D-L test which the authors did not test. This means they did not prove specificity for the D-L reagent test.. Nonetheless, the authors claimed that: “The specificity of the Duquenois reaction has been established, empirically at least, over the past three decades. No plant material other than marijuana has been found to give an identical reaction.” They added that: “The original Duquenois reaction was adopted as a preferential test by the League of Nations Sub-Committee on Cannabis (Duquenois, 1950). A modification of the test has been proposed by the United Nations Committee on Narcotics (1960) as a universal and specific test for marijuana. The modification referred to is the addition of chloroform to the final colored complex, a technique suggested by the U.S. Treasury Department Bureau of Narcotics (Butler, 1962) This modification of the test would seem to insure the specificity of the reaction, as the reactive phenolic materials other than the constituents of marijuana resin do not give colors soluble in chloroform. This has lead [sic] the UN Committee on Narcotics to conclude that there is nothing other than marijuana which will give exactly the same Duquenois reaction (Farmilo et al, 1962).” All of these assertions have now been proven false. (Whitehurst 2009)

As was the case with the NIST sponsored study, the article itself cannot be legitimately cited by drug analysts or prosecutors because the D-L test is subjective since it depends on the color discrimination of the tester. As noted above, subsequent to its publication, scores of substances were found to render false positives with the D-L test, and the UN declared that the D-L test was only a screening test and that the only valid test for marijuana and cocaine is GC/MS.

The devastating effect of admitting conclusory reports and the results of nonspecific drug tests such as the D-L test as evidence has been eloquently enunciated by Professor Edward Imwinkelried. He wrote: “It is not only unnecessary for the courts to accept conclusory drug identifications based on nonspecific tests, it is also unwise for them to do so. The essence of the scientific method is formulating hypotheses and conducting experiments to verify or disprove the hypotheses. A proposition does not become a scientific fact merely because someone with impressive academic credentials asserts it is a fact. Testimony should not be treated as an expert, scientific opinion without a truly scientific basis, such as experimentation. Conclusory drug identification testimony is antithetical and offensive to the scientific tradition, and courts should not allow ipse dixit to masquerade as scientific testimony.(Kelly 2008)

A glaring example of intellectual dishonesty and a judicial imprimatur on bad science and bad law was Judge William Alsup’s admission into evidence of the results of the microscopic and D-L tests in the U.S. v. Diaz case in San Francisco. Section 702 of the Federal Rules of Evidence assigns to district courts the role of gatekeeper and charges the courts with assuring that expert testimony and forensic tests rest on a reliable foundation and are relevant to the task at hand In Daubert v. Merrell Dow Pharmaceuticals, Inc, the Supreme Court created a flexible, factor-base approach to analyzing the reliability and validity of forensic tests and expert testimony. These factors include: (1) whether a method can or has been tested; (2) the known or potential rate of error; (3) whether the methods have been subjected to peer review; (4) whether there are standards controlling the technique’s operation; and, (5) the general acceptance of the method within the relevant community. The Supreme Court further explained that a district court has "considerable leeway in deciding in a particular case how to go about determining whether expert testimony is reliable."11

As explained in the book, Fitness for Purposes of Mass Spectrometric Methods of Substance Identification: “Moreover, it must be realized that a ‘positive’ confirmation test thus obtained is not an unambiguous identification of Y (unknown substance). It only shows that the test result is not against the presumptions. Other substances may be able to give results that are the same or indistinguishable from those of Y. Therefore, unambiguous identification of Y is achieved if all other (relevant) substances can be excluded, so that Y remains the only possible candidate [even] if one focuses only on those that have some relevance to the field of analysis [data] on thousands of substances per field is necessary.”12

The inadequacy of the D-L test has been noted by Armaki and his co-authors, "the unsatisfactory color tests [named] Beam, Duquenois, and Chamrawy … lack in adequate specificity…" Turk and his co-workers also reported that "the presently used colorimetric tests respond to a variety of vegetable extracts and to certain pure substances (i.e. false positives)." R.N. Smith found that 12 of 40 plant oils and extracts gave a positive D-L test. M.J. de Flaubert Maunder further questioned the reliability of the D-L test per se by stating that it depended on the subjective judgment of the analyst. "[A] positive test," he wrote, "is not recorded until this color (pink/mauve) has been identified, and because it is almost impossible to describe in absolute terms it is best recognized by experience, as are the color transitions in the acid solution."

A chemical identification test should be independent of the experience or judgment of the analyst as long as the analyst knows how to correctly carry out the test and follow the protocol. Otherwise, a second analyst could not necessarily replicate the procedures and findings of the first analyst. Maunder further reported a number of substances which "gave a red to blue chloroform solution which, without careful observation of the speed and sequence of color development after the addition of the acid, may be difficult to distinguish from the cannabis color. None of these materials gave precisely the same color behavior as fresh cannabis, but most could not be readily distinguished from the reaction with old, or trace amounts, of cannabis."1

Maunder found another difficulty with the D-L test when the suspected substance is powdery or sticky. He reported that in this case, one will get a false positive for marijuana, if one does not use two thicknesses of absorbent paper and sufficient petroleum ether (PE) to moisten the lower paper and apply the test to the lower paper. "If the PE solution is not filtered in this manner," he wrote, "most powders will leave enough residue on the paper to give sufficient water soluble material for a false positive."13

C.G. Pitt wrote in his conclusion “it is believed that if the criteria for a positive Duquenois test are rigorously adhered to, and botanical evidence is not available, the ubiquitousness of phenols in nature and their diversity in structure makes it mandatory to supplement the colorimetric test with chromatographic evidence. This conclusion is substantiated by the recent report that certain commercial brands of coffee give a positive Duquenois-Levine test." Pitt added that the D-L test is useful as a "screen" test but not sufficiently selective to be relied upon for "identification." 14

As noted, in Daubert v. Merrell Dow Pharmaceuticals, Inc, the Supreme Court created a flexible, factor-base approach for analyzing the reliability and validity of forensic tests and expert testimony. These factors include: (1) whether a method can or has been tested; (2) the known or potential rate of error; (3) whether the methods have been subjected to peer review; (4) whether there are standards controlling the technique’s operation; and, (5) the general acceptance of the method within the relevant community. Crime labs do not test or validate the D-L methods, has no error rates established, has not subjected them to peer review, and does not exercise controls or standards with this level of drug testing.

The Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG)15 also stipulates that:

“When a category A technique (instrumentation such as mass spectrometry) is not used, then at least three different validated methods shall be employed . . . Two of the methods shall be based on uncorrelated techniques from Category B (includes thin layer chromatography and for cannabis only, macroscopic examination and microscopic examination . . . A minimum of two separate samplings should be used in these three tests … All Category B techniques shall have reviewable data . . . Cannabis exhibits tend to have characteristics that are visually recognizable. Macroscopic and microscopic examinations will be considered, exceptionally, as uncorrelated techniques from Category B when observations include documented details of botanical features . . . Examples of reviewable data are . . . recording of detailed descriptions of morphological characteristics of cannabis only . . . Laboratories shall have documented policies establishing protocols for technical and administrative review . . .

“Method validation is required to demonstrate that methods are suitable for their intended purpose. For qualitative analysis, the parameters that need to be checked are selectivity, limit of detection and reproducibility . . . Minimum acceptability criteria should be described along with means for demonstrating compliance. Valid documentation is required. Laboratories adopting methods validated elsewhere should verify these methods and establish their own limits of detection and reproducibility.”

According to Standard Practice for Quality Assurance of Laboratories Performing Seized-Drug Analysis of the American Society of Testing Materials, “Analysts shall take measures to be assured that identifications are correct and relate to the right submission. This is best established by the use of a least two appropriate techniques based on different principles and two independent samplings. Documentation must contain sufficient information to allow a peer to evaluate the notes and interpret data.” Also according to According to the United Nations Division of Narcotics’ Drugs Recommended Methods for Testing Cannabis:

“When possible, three entirely different techniques should be used, for example, color test and any two of the available chromatography techniques (TLC, GLC, or HPLC). The analysis of cannabis represents a special problem to the forensic chemist.” According to the UN’s Recommended Guidelines for Quality Assurance and Good Laboratory Practices: “Before an analytical procedure can be used to analyze submitted specimens, it must be fully validated in terms of sensitivity (limits of detection), specificity (freedom from interferences), and reproducibility (ability to provide consistent results)…. Before a specimen can be reported positive for one or more drugs of abuse, it should be subjected to two independent tests using separate aliquots of the specimen. If feasible, the two tests should involve different analytical techniques. Specific criteria for what constitutes a positive test should be established and clearly stated in the SOP manual. The criteria should include requirements for acceptable results and quality control samples. Also, before any specimen can be reported positive, the test results should be thoroughly reviewed by at least two individuals who are familiar with the analytical methods. The review should include examination of the test results, acceptability of all quality control results, proper and complete documentation of sample handling (chain of custody), correct calculation of quantitative measurements and absence of clerical error . . . undeclared or ‘blind’ proficiency testing (is recommended).”

The UN’s Rapid Testing Methods of Drugs of Abuse adds that: “Colors formed by the test reagents should be compared with a color reference chart if possible because color evaluation by individuals is a subjective judgment and can lead to misinterpretation of results.” The Scientific Working Group for the Analysis of Seized Drugs’ Quality Assurance/Validation of Analytical Methods agrees with the UN on this point: “Since the results of color tests are detected visually, care must be taken that the analyst be thoroughly tested for the visual ability to detect very slight color changes.”18

The heart of scientific method verification relies on reviewability and reproducibility. In regards to the Supreme Court’s ruling in Daubert v. Merrell Dow Pharmaceuticals, Inc., the Ninth Circuit court declared: “Something doesn’t become ‘scientific knowledge’ just because it’s uttered by a scientist nor can an expert’s self-serving assertions that his conclusions were ‘derived by the scientific method’ be deemed conclusive, else the Supreme Court’s opinion could have ended with footnote 2. As we read the Supreme Court’s teaching in Daubert, therefore, though we are largely untrained in science and certainly no match for any of the witnesses whose testimony we are reviewing, it is our responsibility to determine whether those experts’ proposed testimony amounts to ‘scientific knowledge,’ constitutes ‘good science,’ and was ‘derived by the scientific method.’” Additionally Judge Kozinski’s Ninth Circuit opinion regarding Daubert noted that the court must decide in part whether the scientists have derived their results and findings through the scientific method or whether their testimony is based on scientifically valid and accepted principles. (Daubert, 43F.3d at 1316). The gate keeping role of the court should view reliability as follows: ‘This means that the expert’s bald assurance of validity is not enough. Rather, the party presenting the expert must show that the expert’s findings are based on sound science, and this will require some objective, independent validation of the expert’s methodology.”

Recent court rulings have disagreed that this test needs specificity and exclusivity and that the tester’s experience allows these results to be admissible. It is well recognized in the scientific community that an analytical test stands on its own, independent of the analyst and their experience. It is not the experience of the analyst that adds or subtracts from the validity and acceptance of the test for admissibility of evidence.

Part 2: Chemical Defense Revolution: Death by Odor Perception

The 4th Amendment of the United States Constitution protects American citizens against unreasonable search and seizure without probable cause. Probable cause for search and seizure occurs when known facts and circumstances of a reasonably trustworthy nature are sufficient to justify a person of reasonable caution and prudence in the belief that a crime has been committed (Draper v United States, 1959). This is a common definition in most common legal textbooks. The subjective nature of this definition becomes problematic upon practical application. This can be particularly troubling when the sensory perception of weak odors becomes the basis for search.

Law enforcement officers often justify their searches with their sense of smell when other more tangible criteria are not present. This type of encounter often occurs when the odor of marijuana is the basis for probable cause for entering vehicles and dwellings to search for illicit drugs (United States v. Boger 1990, United States v. Reilly 1994, United States v. Shates, 1995). Unfortunately very little research exists on the human capacity to detect marijuana’s odor in a laboratory or in real-life situations, despite its widespread use by law enforcement. This absence of information bears considerable legal consequence due to the fact that courts often accept the argument, prima facie, the odor of marijuana can always be detected. United States v. Harris in 1994 is one such example where police officers reported the smell of marijuana and the search revealed only cocaine. This case illustrates the issue that needs to be addressed concerning the use of smell for probable cause.

It is generally believed that the odor characteristic to marijuana can be discerned from a variety of C. Sativa plants, regardless of their geographic origin, strain, extent of processing, and tetrahydrocannabinol (THC) content and yet there is a disturbing absence of quantitative information on this topic.

Doty et al (2004) performed studies stemming from the need to better understand the nature of marijuana’s odor and whether humans can discern this odor in situations modeled from “real-life” law enforcement encounters. The first series of experiments investigated a situation in which an arresting officer reportedly discerned processed marijuana within an automobile trunk from the passenger compartment. Initially Doty et al set out to determine whether the marijuana odor was discernable through the walls of a plastic bag containing marijuana. Upon confirmation at that point they determined whether this discernment could take place inside the passenger compartment of a car when the trunk contained the same package of marijuana.

The second set of experiments was based on a situation present in an illicit marijuana grow house in northern California. Odors from the immature Cannabis Sativa plants were combined with diesel exhaust from a generator and expelled through a chimney. Law enforcement officials reported being able to smell the marijuana from a road that was several hundred yards away and subsequently used this odor as probable cause for a search. This second set of studies was to determine whether the odor of immature marijuana plants differ in quality or intensity from that of mature marijuana plants. They then investigated whether the marijuana odor was distinguishable from a mixture emanating from immature C. sativa plants combined with diesel engine exhaust. Doty, Wudarski, Marshall, and Hastings in “Marijuana Odor Perception: Studies Modeled From Probable Cause Cases” published in Law and Human Behavior, Vol. 28, No. 2, April 2004 presented the following:

EXPERIMENT 1 - Study 1

The purpose of this study was to determine whether a group of men and women could distinguish the odor of packaged marijuana from that of a matched blank odor source.


Participants. Five men and four women recruited from advertisements placed on community bulletin boards served as participants. None reported being a smoker of marijuana, and all were nonusers of tobacco products. Most were in their “20s” (median = 27 years) and all reported being in good general health. All were medication-free, and scored within normal limits on the University of Pennsylvania Smell Identification Test (UPSIT), a standardized olfactory test (Doty, 1995; Doty, Shaman, & Dann, 1984).

Test Procedures. Prior to formal testing, the participants familiarized themselves with the odor of a sample of processed Mexican marijuana supplied by the New Jersey Attorney General’s Office. A State law enforcement official was present during the testing and was custodian of the marijuana. Formal testing was performed in a 14 £ 17 ft2 room with excellent air circulation. Each participant was blindfolded and led in one at a time at approximately 5-min intervals, at which point they were asked to sniff two garbage bags in succession (“Hefty” brand, 2-ply, 1.5 mil). One contained five 1-pound packets of pressed and processed Mexican marijuana and the other newspapers crushed and bundled in a similar fashion. Each participant was then required to report the bag that smelled most like marijuana. Half of the participants received the marijuana-containing bag first, so as to counterbalance test order.


All nine participants reliably and unequivocally reported the garbage bag containing marijuana to have a marijuana-like smell, and none reported the control garbage bag as having such an odor (Binomial test, p .20).


Experiment 2 was conducted in a state sanctioned medical Cannabis growing facility in Northern California. We first addressed whether non budding and budding marijuana plants produce similar odors. We then investigated if low levels of diesel exhaust fumes could mask the odor of immature marijuana plants.

Study 1


Participants. Five men and one woman, ranging in age from 20 to 57 (M = 41.5 years, SD = 14.3), served as participants. These individuals were recruited by word of mouth from the neighborhood surrounding the California grow facility, and all reported being in good general health. All exhibited above average smell function, as measured by the UPSIT (Doty, 1995; Doty, Shaman, & Dann, 1984) Stimuli and Test Procedures. The test stimuli consisted of four immature (non budding) female Cannabis plants, one mature (budding) female Cannabis plant, one female tomato plant (Lycopersicon), and one empty container containing planting soil. Only one mature Cannabis plant was used because the odor from this Cannabis plant was distinctive. Female plants were used because they produce more flower biomass than male plants, and are preferred by marijuana growers. Cannabinoids, such as 19- tetrahydrocannabinol, tend to be particularly concentrated in the flower related bracts (Turner, Hemphill, & Mahlberg, 1980).

Polyethylene bags with no discernable odor were placed over each of the plants or the planting pot containing soil. The bags were positioned to collect the vapors emanating from the plant and associated potting soil. These vapors were sniffed by participants through a 20-cm long, 2.54-cm odorless PVC tube inserted through a slit in the bags. The temperature of the room in which testing occurred was »21±C.

Although all six participants indicated that they were aware of the smell of marijuana, we provided a sample to ensure familiarization with the odor. The participants were not informed of the positioning of the stimulus pots on the sampling table, and wore opaque goggles to preclude visual input.

Each participant was guided to the stimulus plant by an experimenter, who inserted the tube into the plant environs. The experimenter then positioned the participant’s hands on the tube so as to enabling them to sniff through its end. The order of smelling the stimuli was systematically counterbalanced both between participants and within trial sessions of the same participant to preclude confounding by order effects. At least 45 s was interspersed between trials to minimize possible adaptation effects. The sniffing tubes were also cleaned with ethanol and water after use to eliminate any residual odors that accumulated during the test session.

The task of the participants was to report not only whether or not marijuana odor was present, but to quantitatively compare the relative intensity of the total odor using a magnitude estimation procedure. In this procedure odors are related relative to one another without a standardized scale (termed the free-modulus method). Because magnitude estimation numbers are ratio in nature, an assignment by a given participant of 25 to a stimulus theoretically is perceived half as intense as an assignment of 50. This method is well documented in the psychophysical and organoleptic sensory literature (Doty, 1975; Marks, 1988; Moskowitz, Dravnieks, Cain, & Turk, 1974). The judgments were collected on three separate occasions, resulting in a total of 126 trials within the whole study. The median of the three intensity judgments for each participant was used as the intensity test measure.


The identification data of the six participants revealed that: (i) the mature Cannabis plant was always rated as having a characteristic marijuana odor; (ii) three of the four immature Cannabis plants never were found to have a distinctive marijuana odor; (iii) one of the four immature Cannabis plants was always rated as having a marijuana-like smell; and (iv) the potting soil alone was always reported as having an odor, but never as having a marijuana-like odor.

The median magnitude estimates of the odor intensity for the potting soil, immature marijuana, mature marijuana, and tomato plant stimuli were calculated, and because magnitude estimation numbers are arguably ratio in nature, we determined ratios of the rated intensities relative to the baseline estimates of potting soil. These ratios are presented in Table 2.

Study 2

The purpose of Experiment 2 was to determine whether diesel exhaust odor could mask the odor of volatiles from Cannabis sativa L under a specific set of “real world” circumstances. We aimed to conservatively model, within reasonable bounds, a situation present in the aforementioned California grow room where the exhaust of volatiles from immature Cannabis sativa plants were combined with diesel exhaust from a generator and expelled outside through a chimney. In effect, we sought to determine whether the odor of marijuana volatiles could be discerned from the background of diesel exhaust odor under conditions similar, or even more stringent, to those in this specific situation.


Participants. Five of the 10 participants in this experiment were the male participants of Study 1. One new participant was a female and the other four new participants were male. The UPSIT was administered to three of these additional individuals and all were within normal limits. The remaining participants reported no problems smelling, although their sense of smell was not formally evaluated. Three of the five new participants reported having intimate knowledge of the smell of marijuana and admitted to being occasional or regular marijuana smokers.

Procedures. We employed an olfactometer capable of providing, for nasal sampling, a mixture of diesel exhaust and Cannabis volatiles in the relative proportions estimated to have been present within the chimney effluence of the illicit marijuana grow room (see Fig. 1). In this system, clean room air was pumped into two identical 114-l galvanized steel chambers at a rate of 68 l/min. In one of the 114-l chambers, two marijuana plants (»38 cm high) were situated; the other housed identical containers and potting soil, but no plants. To produce and maintain a temperature in these chambers equivalent to that present in the illicit grow room (approximately 27±C), digital temperature probes and 150-watt light bulbs were placed within them. The chamber temperatures were continuously monitored and the intensity of the light bulbs adjusted via a rheostat to maintain the temperatures at the desired level (range: 25± ± –28 C).

It should be noted that the two Cannabis plant employed in this study were selected from a larger number of similar plants available to us at the growing facility. We did not wish to bias the selection procedure, so none of these plants had been previously smelled. Each was assigned a number, and the two numbers chosen were determined using a random process.

The output of the olfactometer was channeled through a PVC pipe to a sampling port from which the participants made their observations. During the intertrial intervals, the test mixture was directed from the sniffing port. The basic parameters that had to be met or exceeded in the simulation were derived from measurements of the illicit California grow room and were as follows: (i): the volume of the air in the grow room (190.5 m3); (ii) the number of immature plants reportedly housed in the grow room (440); (iii) the air flow through the grow room (calculated at 65.14 l/min); and (iv) the empirically determined flow rate of diesel engine exhaust (3.8 m ± per minute at 19 C). The degree of dispersion of chimney effluent into the ambient air, which would dilute the effluent considerably and make detection even more difficult, was not included in the model.

In the original situation, one plant occupied 0.43 m3. However, the plants in the original illicit grow room were somewhat larger than those available to us for study. Therefore, because one plant originally occupied 0.43 m3, we placed two plants in the galvanized steel container (114 l). This provided a cushion of error to compensate for differences in plant density and any minor errors that may be present elsewhere in the model (e.g., differences between actual and measured flow rates). Additionally, a higher ratio of marijuana (or potting soil chamber) air to diesel exhaust effluent was employed to make even more conservative the test as to whether marijuana odor could be discerned within diesel exhaust.

The psychophysical paradigm consisted of 20 test trials given to 17 of the test participants. The number of trials of three participants was abbreviated because of schedule conflicts, resulting in 19 trials in two cases and 15 trials in the remaining case. In sum, 193 total trials were completed in the experiment. On half of the trials the diesel exhaust was presented with no marijuana odor (i.e., just the odor of potting soil), and on the other half the diesel exhaust was presented with the volatiles emitted from the marijuana plants and their potting soil. After switching the valves to a new test condition, 3–5 mins were allowed to pass before testing commenced to insure adequate purging of the odors from the previous test condition.

The entire test session lasted approximately 3 hr. Each participant was tested individually and was instructed not to discuss his or her responses with the other participants. No information regarding the probability of a marijuana trial relative to a blank trial was provided. All participants received testing on a specific trial before the olfactometer was reset for the next trial. The task of each participant on each trial was to answer two basic questions: (i) do you smell diesel exhaust?; and (ii) do you smell marijuana odor?


No convincing evidence was present in the data that any of the participants could reliably detect the marijuana odor embedded in the diesel fumes. A one-sided Fisher exact probability test revealed no meaningful difference between the hit (6 of 96 trials) and false positive (3 of 96 trials) rates, implying that this level of responding to the diesel + marijuana vapor stimulus is within a range expected by chance. Hence, the data provided no statistical support for the notion that human participants can discern marijuana odor from diesel odor under the conditions of this experiment.

The results of the studies done by Doty et. al. were under limited and specific conditions and they in fact note that the results of these experiments should not be generalized to other seemingly similar events. It should also be noted that under varying temperature conditions can affect the diffusion of molecules from plants. An inability to detect marijuana in the trunk of a car may be different on a hot summer day than on a cold winter day. There are other factors that may need further examination such as gender, age, and training for recognition of odors. Standardized procedures, just as established for canines, are needed to establish smell ability for those that are called to testify about odors of illicit drugs. It is also important not to overlook that expectation or power of suggestion can often dictate the likelihood of a person believing that they can smell an odor which is a common problem in environmental annoyance issues.


This leaves us with a series of thoughts to ponder: 1) The validity of law enforcement officers using the sense of smell to discern the presence of marijuana and should the practice of this sensory application without validation suggest a blanket acceptance of testimony? 2) Should we be overlooking the lack of validity for the method of presumptively identifying leafy greenish-brown vegetable matter to be marijuana and allow the acceptance of testimony without confirmatory testing? 3) How far can we stretch FRE 702? 4) With the error rate approximately 25% of non-marijuana substances yielding false positives for the D-L test as shown by Dr. Omar Bagasra in 2008, what margin of error exists in the field?

Cases of Misidentification:

March 2009 – The Birdwatcher

An avid bird-watcher, she brought her sage along for smudging, a purification ritual popular among Native American tribes and spiritual groups. She believes the smoke from the sage helps clear negative energy and also helps take your prayers to heaven. Before heading back to her car, she burned the sage in a clay pot to give thanks for the wildlife she had seen that day.

"Smudging is a way for me to give thanks and express my gratitude," she said. "That day, I was using it to carry my prayers to heaven." When she returned to her car, a deputy and officer with the Fish and Wildlife Conservation Commission were waiting. They asked what she was doing there.Bird-watching, she told them. When they continued to question her, she opened her backpack to show them her binoculars and bird book.

That's when the deputy spotted her sage and the smudging bowl with burned ashes.
A Sheriff's Deputy mistook sage for marijuana, then searched her car and found more. His field kit said the sage — purchased at an airport gift shop in Albuquerque, N.M. — tested positive for marijuana.

He did not arrest her that day in March 2009, but sent the 50 grams of "contraband" to the crime lab for a more definitive test. Assistant State Attorney ordered an arrest without having the sage tested, court records show. Three months later, the Deputy showed up at her place of employment and took her away in handcuffs.

A month later, her attorney discovered that the sage had never been tested at the Sheriff's Office crime lab whereby he ordered a confirmatory test be performed. The lab test concluded that the dried sage was not marijuana at all. The criminal charges were dropped.

August 2008 – Natural Chocolate and Super Foods

(NaturalNews) When Ron and Nadine from the Living Libations beauty care and chocolate company ( attempted to fly to the United States in August of this year, they ran into something completely unexpected: Drug-sniffing dogs at the Toronto airport. When their dogs took a special interest in their raw, unrefined chocolate with hemp seeds and superfood extracts, they were arrested, handcuffed and put through hours of tortuous interrogation. Such begins the journey of Ron and Nadine, the chocolate freedom fighters from Canada.

Accused of trafficking two and a half pounds of hashish (which was really just raw, homemade chocolate), Ron and Nadine were arrested, physically separated into interrogation rooms and handcuffed to chairs. Their six-month old baby was forcibly taken from them, and they were immediately subjected to intense interrogation.

Their chocolate looked suspicious, they were told, because it wasn't in a commercial wrapper. If it's not Hershey's, it must be drugs! An on-the-spot drug test from the NIK company (which makes portable drug testing kits) returned a positive result, the Canadian police claimed, and that's all the evidence they need to arrest anyone.

Thus we can see that questionable practices are in existence and as well conflicting policies and court decisions as regards to testing for controlled drugs and admissible evidence under the Supreme Court decision of Daubert. This is manifested in forensic falsehoods and directly contradictory of judicial opinions and decisions across and within jurisdictions. The result of all of this is an unconstitutional lack of equal justice under the law for suspected and convicted drug offenders.


1. Kelly, J. 2008 “False Positives Equal False Justice”
2. Thornton, J.I. et al, “The Identification of Marijuana”, 12J. Forensic Sci. Soc. 461, 462 (1972)
3. Nakamura, G. R., Forensic Aspects of Cystolith Hairs of Cannabis and Other Plants, Drug Abuse Control, 52 J. Association of Official Analytical Chemists 5,5 (1969)
4. Tindall, C. et al, Methods of Forensic Analysis in The Handbook of Forensic Drug Analysis 43,43 (Frederick P. Smith ed. 2005)
5. Whitehurst, F. 2009 Texas Law Review, Vol. 41:1; “Forensic Analysis of Marijuana and the Kurzman Mystery: A Case Study of Flawed Logic in Determination of Guilt”.
6. Stahl, E. et al, Drug Analysis by Chromatography and Microscopy 1973.
7. Thorne, R. F. “How Many Species of Seeds Plants are There?”, 2002
8. O’Neal, C. L. et al, Validation of Twelve Chemical Spot Tests for the Detection of Drugs of Abuse, 109 Forensic Science International, (2001) 189-201.
9. Color Test Reagents/Kits for Preliminary Identification of Drugs of Abuse NIJ Standard 0604.01, US Department of Justice/Office of Justice Programs, National Institute of Justice/Office of Technology NCJ 183258 (July 2000) 1-13.
10. Seigel, J. Forensic Science: The Basics 1st Edition
11. USA v. Edgar Diaz et al No. CR05-0167 WHA US District Court for the Northern District of CA, 2006 US Dist. LEXIS 910684
12. De Zeeuw, R. A., Fitness for Purposes of Mass Spectrometric Methods in Substance Identification, Journal of Forensic Science 50:3 May 2005
13. Maunder, M.J. “Two Simple Color Tests for Cannabis, UNODC Bulletin on Narcotics”, Issue 4-005 (1969), 37-42
14. Pitt, C. G. et al, “The Specificity of the Duquenois-Levine Color Test for Marijuana and Hashish”, Journal of Sciences 17(4) (1972) 693
15. Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) Recommendations, US Department of Justice, DEA, 2nd Edition, 2006-07-09
16. Annual Book of ASTM Std. 2006 Section 14.02 Designation: E2327-04 Standards of Practice for Quality Assurance of Laboratories Performing Seized-Drug Analysis.
17. Recommended Methods for Testing Cannabis, Manual for Use by National Narcotics Laboratories, Division of Narcotic Drugs, Vienna ST/NAR/8 (United Nations New York 1987) pp.2-3
18. Recommended Guidelines for Quality Assurance and Good Laboratory Practices, united Nations Division of Narcotic Drugs, Vienna (1992) pp. 23,25, 29
19. Draper v United States, 358 US 307, 795, ct.329, 3L.Ed.2d327 (1959)
20. United States v Ronald Boger, 755F. Supp.333 (1990)
21. United States v Deborah Ellis, 15F Supp. 2d 1025 (1998)
22. United States v Norris Shates, 915F. Supp 1483 (1995)
23. Doty, R. et al, “Marijuana Odor Perception: Studies Modeled from Probable Cause Cases”, Law and Human Behavior, Vol.28, No. 2, April 2004

Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer. For specific technical or legal advice on the information provided and related topics, please contact the author.

Find a Lawyer

Find a Local Lawyer