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4 The Open Forensic Science Journal, 2012, 5, 4-8
1874-4028/12 2012 Bentham Open
Open Access
The Non-Specificity of the Duquenois-Levine Field Test for Marijuana
John F. Kelly*,1, Krishna Addanki2 and Omar Bagasra*,2
11832 Biltmore Street NW Apt 35 Washington DC, 20009, USA
2South Carolina Center for Biotechnology, Claflin University, Orangeburg, SC 29115, USA
Abstract: The purpose of this study is to determine the specificity, or lack thereof, of the Duquenois-Levine (D-L) field
test kit in the identification of marijuana. Out of the forty-two samples tested, patchouli, spearmint, and eucalyptus tested
positive for marijuana u sing the D-L field test. From these results, it can be concluded th at the test is non-specific and can
yield false positives. Therefore, it cannot be legitimately used for the prosecution or conviction of an individual for
violations of the anti-marijuana laws as it does not provide proof beyond a reasonable doubt of the presence of marijuana.
In fact, law enforcement personnel and the test kit manufacturer claim that the D-L field test is a specific, identification
test with near perfect accuracy. In court, police officers testify falsely to the identification of marijuana in a seized
substance based solely on the D-L test and other non-specific, screening tests leading to convictions. The result is the
denial of the Constitutionally-guaranteed right to a fair trial, due process and countless wrongful marijuana convictions.
Keywords: Duquenois-Levine field test, False positive, Marijuana, NIK pouch test.
INTRODUCTION
There are no published studies on the specificity of the
Duquenois-Levine (D-L) field test or its capacity to render
false positives. Manufacturers until recently have claimed
that the test does render false positives, and therefore does
not identify marijuana per se. But this assertion was not
based on a published study. In 1996, Captain Allan C.
Rothberg of the Philadelphia Police Department reported
that in 1986, he, in conjunction with the DEA and the NIK
field test manufacturer, had transformed controlled substance
field tests into specific identification tests. “With well over
100,000 field tests (which included cocaine and heroin tests
as well as marijuana tests) done to date”, he wrote, “the
accuracy has never dropped under 99+%” [1]. Rothberg
provided no explanations or data to support his claim either
in his unpublished report or when he was contacted by us.
When we contacted the manufacturer in 2010, we were told
that: “Independent testing has shown the presumptive test
kits are about 99% reliable” [2]. The so-called independent
testing cited by the manufacturer was Captain Rothberg’s
report as well as sworn affidavits and testimonies by law
enforcement personnel that the (D-L) test does not render
false positives. For instance, Terry Mills, while Supervisor
of Drug Identification for the Georgia Bureau of
Investigation, claimed to have never found a false-positive in
more than 1,000 D-L tests [3]. Susan Hart Johns, while a
drug analyst for the Illinois State Police, swore she found no
false positives in 3-4,000 D-L tests [4]. As with Rothberg,
there were no data to support these assertions.
However, it was theoretically possible that the D-L field
test as opposed to the lab test was specific and did not render
*Address correspondence to these authors at the South Carolina Center for
Biotechnology, Claflin University, 400 Magnolia Street, Orangeburg, SC
29115, USA; Tel: +803-535-5253; Fax: +803-535-5776;
E-mails: obagasra@claflin.edu, kjohn39679@aol.com
false positives since no one had experimentally tested the field
test. To address this question, we conducted the following
experiments with both the D-L and KN Reagent field tests.
MATERIALS AND METHODS
In 2008, the NIK NarcoPouch 908 D-L field test kit was
used to analyze numerous non-marijuana substances (including
plant extracts, chocolate, medications, etc.) following the
prescribed procedures by NIK which are as follows:
1. Remove clip, insert suspect material into test pack,
reseal with clip and tap gently to assure material falls
to the bottom of pack.
2. With the printed side of the test facing you, break
ampoules from left to right. Break by squeezing the
center of the ampoule with tips of thumb and
forefinger.
3. Break left ampoule, agitate vigorously for at least one
minute.
4. Break middle ampoule and agitate gently. A blue-
violet or purple color will develop within a few
seconds to a minute if marijuana is present. Allow
sufficient time for the blue-violet or purple to
develop, but do not allow it to become too dark.
5. As soon as the blue-violet or purple color develops,
break the right ampoule. Tap the pouch once or twice
and the blue-violet or purple color will be extracted
into the lower layer. Upper layer color is unimportant.
6. The formation of the proper blue-violet or purple
color and its extraction into the lower layer is a
positive test for marijuana.
RESULTS
Patchouli, cypress, and eucalyptus tested positive for
marijuana; while lavender, spearmint, oregano, and thyme
gave inconclusive results. All other non-marijuana
The Non-Specificity of the Duquenois-Levine Field Test for Marijuana The Open Forensic Science Journal, 2012, Volume 5 5
substances including Hershey’s chocolate, over the counter
medicine and a few detergents tested negative. Below are the
pictures of Positive, False Positive, Inconclusive, and
Negative test results. (See Fig. (1), Positive Result, False
Positive Result, Inconclusive Test Result of Spearmint with
D-L Test Image, Negative Test Result of Olive Oil with D-L
Test Image).
DISCUSSION
The NarcoPouch 908 D-L field test kit was found to be
nonspecific and subjective. The positive testing of patchouli,
spearmint, and eucalyptus for marijuana demonstrates the
ability of this field test k it to produce false positives.
Addition ally, inconsistent and inconclusive testing results of
lavender, cypress, and oregano demonstrate that the results
of this field test are at the discretion of the tester’s colo r
discrimination abilities. In other words, the “proper blue-
violet or purple” color which yields a positive test for
marijuana is different for each testing official; what is blue-
violet or purple enough for a positive test result to one
official may not be blue-violet or purple enough for another.
This means the field tests cannot be legitimately used to
identify marijuana in a seized substance. The significance of
this finding cannot be over emphasized particularly in light
of the fact that police officers around the country now testify
and “identify” the presence of marijuana in a seized
substance solely on the basis of mariju ana field tests such as
the D-L. Since the D-L field test cannot identify the presence
of marijuana, this raises the serious possibility of tens of
thousands of wrongful drug convictions.
Moreover, the DEA now claims that the D-L test does
not render false positives and is “error-free”, according to
recent testimony by DEA senior chemist Heather Hartshorn
[5]. Judge J. William Ryan called her testimony “ridiculous
on its face’ and noted that: “Any claim of infallibility is
troubling. ‘Scientists, along with all other individuals,
Fig. (1). (a) Positive Test Result. The image is a result obtained on testing marijuana. The formation of the proper blue-violet or purple
color and its extraction into the lower layer d emonstrates a positive test result for marijuana using the D-L Test. (b) The image is a result
obtained on testing Patchouli Plant Extract. The formation of the proper blue-violet or purple color and its extraction into the lower layer in
both cases demonstrates a positive test result for Patchouli Plant Extract using the D-L Test. (c) Inconclusive Test Result of Spearmint
Plant Extract with the D-L T est. The image is a result obtained on testing Spearmint Plant Extract Two distinct layers are present;
however, the color in the top layer is brownish purple and the color in the bottom layer is brown thus rendering an inconclusive test result.
(d) Negative Test Result with Olive Oil. The image is a result obtained on testing Olive Oil Plant Extract The absence of a blue-vio let or
purple color demonstrates a negative test result for marijuana.
6 The Open Forensic Science Journal, 2012, Volume 5 Kelly et al.
evidence cognitive limitations that lead to frequent judgment
error and that set surprisingly harsh restrictions on the
capacity to manage complex information and to make
decisions.’ (David Faust. The Limits of Scientific Reasoning,
1, U. Minn. Press, 1984). Further, it is beyond cavil that such
a claim of infallibility is anathema to th e essence of science
as understood in the last 100-plus years. Thomas Kuhn and
Karl Popper, contemporary philosophers of science whose
conceptions of the nature of science represent opposite-ends
of the current spectrum, the former’s scientific revolutions-
as-paradigm-to-anomalies-to-revolution versus the latter's
perpetual subjection of theory to falsif iability/testability, as
well as thinkers a century-prior, all point to error as an
inherent component of the scientific endeavor. (E.g., Popper,
K.R., Conjectures and Refutations: The Growth of Scientific
Knowledge, 116-117, Basic Books, 1963 (“[O]ur latest and
best theory is always an attempt to incorporate all the
falsifications ever found in the field, by explaining them in
the simplest way; and this means ... in the most testable
way”); Nietzsche, F.W. (“There are no facts, only
interpretations”) [6].
Hartshorn presented no data to support her claims of
infallibility but persisted in her testimony that the D-L test in
concert with two other screening tests is error-free as well as
her testing. Combining screening tests does not add up to a
specific identif ication test. Each retains its own non-
specificity and error rate, and even if each test is positive for
marijuana, each one could be a false positive. Hartshorn
admitted that the D-L and th e other two tests in isolation
rendered false positives. But when they are combined they
are error free as is her testing. This is possibly perjury
especially since at least two DEA studies, including one at
her lab that found a 20% error rate, have reported that the D-
L test renders false positives [7] and what she claimed is
scientifically impossible.
Hartshorn’s unsubstantiated claims of infallibility echoed
those of former and current DEA lab directors. For instance,
on April 9, 1999, Joseph P. Bono, then-director of the DEA’s
Mid-Atlantic Laboratory and recent president of the
American Academy of Forensic Sciences, submitted a sworn
affidavit to the courts that all DEA analyses and tests are
“incapable of producing a false positive. . . In other words,
even if the test results are inaccurate, the results will not
indicate the presence of a controlled substance when none is
present in the unknown sample. Even if the instruments used
in the testing are not properly calibrated, if no controlled
substance is present in the exhibit, then no controlled
substance will be identified . . . even when an instrument is
not functioning properly, it will not identify cocaine, or any
other controlled substance, as being present in a sample,
unless that controlled substance is actually present” [8].
Bono’s successor at this lab, Richard Fox, was more
specific in his sworn affidavit which stated, in part, that:
“There is no other plant material that will give a positive
result for all three tests (including the D-L and two other
screening tests) . . . Neither the analyst in this case, nor any
other DEA analyst, has ever misidentified marijuana. . . As
such, the uncertainty measurement associated with the
conclusions reached by the analyst resulting in the
identification of marijuana is zero” [9].
Fox’s successor, James Malone, has testified, in part, as
follows in a marijuana case in Washington, D.C. [10].
Prosecutor: To your knowledge, while you’ve
been at the lab, has the laboratory ever
misidentified a controlled substance?
James Malone: No.
P: Are you aware of anything which shows
that a mis-calibrated system or chromato-
grapher in this case, but any system that was
not calibrated correctly would create a false
positive for cocaine or a controlled substance?
JM: No.
Judge: But Mr. Chawla’s position was, can it
ever - can a mis-calibrated machine ever give
a false positive?
JM: No. A mis-calibrated machine isn’t going
to give you a positive cocaine if there’s not
cocaine.
P: More specifically, if the reagent isn’t
working, is it going to show that the substance
isn’t marijuana? In other words, if the reagent
isn’t working, what’s the result of the
Duquenois-Levine going to be?
JM: It’s going to be negative.
P: Would I get a positive out of a Duquenois-
Levine test? If I used a reagent that wasn’t
working anymore and tried to run a
Duquenois-Levine with that reagent, what
would happen?
JM: You wouldn’t get a false positive, no.
In short, the DEA now claims to have transformed the D-
L test from a 99+% accurate test to a 100% accurate
identification test that renders no false positives. Since DEA
analysts claim to identify marijuana on this basis in court,
this also raises the possibility of tens of thousands of
wrongful marijuana convictions.
Thus, the current positions and operations of law
enforcement personnel and the DEA are a serious concern
and challenge to the legal and forensic science communities
as they defy scientific and legal studies as well as court
decisions that the D-L test alone or in combination with
other tests is non-specific and does not provide
constitutionally-required proof beyond a reasonable doubt of
the presence of marijuana in a seized substance.
The D-L test is actually a combination of two individual
tests. With the Duquenois test, a petroleum ether or
chloroform extract of the plant extract is added to an
ethanolic solution of vanillin and acetaldehyde, followed by
the addition of concentrated hydrochloric acid. Marijuana
gives a deep blue-violet color. With the Levine modification,
the blue-violet test mixture obtained in the Duquenois test is
shaken with chloroform. With marijuana, the blue-violet
color is transferred into th e chloroform layer. However, at
least 50 legal substances have been shown to give the same
color reactions.
The Non-Specificity of the Duquenois-Levine Field Test for Marijuana The Open Forensic Science Journal, 2012, Volume 5 7
As early as 1938, the French pharmacist Pierre
Duquenois, who developed the Duquenois test, found that it
was not specific and gave false positives. Yet, he reported
that the test was specific. Although he claimed it was
specific, he worked to modify the original test into the D-L
test to eliminate false positives which he was unable to d o
[11].
In 1975, Dr. Marc Kurzman et al., conducted a study, in
collaboration with 13 other scientists, which concluded that:
“The microscopic and chemical screening tests presently
used in marijuana analysis are not specific even in
combination for ‘marijuana’ defined in any way” [12].
Regarding the D-L test, Kurzman reported that: “the Levine
modification test has now been proven to be simply a test for
moderate weight molecular resorcinol, common plant
chemical substances. The original Duquenois test was
recognized in the 1960’s as being highly non-specific.
DeFaubert Maunder has reported finding (in a limited plant
sampling) 25 plant species besides Cannabis which will give
a positive Duquenois-Levine test. Smith has also found that
12 of 40 common plant oils and extracts will give a positive
Duquenois-Levine test” [13].
Kurzman, who is also an attorney, proved his conclusion
by winning dismissals and acquittals for his marijuana
defendants on the basis that the tests were not specific and
did not prove the presence of marijuana beyond a reasonable
doubt [12].
The inadequacy of the D-L test has been noted by
Armaki and his co-authors, “the unsatisfactory color tests
Beam, Duquenois, and Chamrawy ... lack in adequate
specificity...” [14]. 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)” [15]. R.N. Smith found that 12 of 40
plant oils and extracts gave a positive D-L test [16].
M.J. de Flaubert Maunder questioned the reliability of
the D-L test per se and of the 240 substances he tested, 25
tested positive for marijuana, i.e. false positives [13].
Maunder himself cautioned that the test “should never be
relied upon as the only positive evidence ...” [13]. C.G. Pitt,
R.W. Hemdron, and R.S. Hsia determined that the D-L test
“is chemically based primarily on the presence of 1,3-
dioxybenzene (resorcinol) partial structure” [17]. In other
words, the D-L test will be positive for many resorcinols -
commonly occurring plant substances and also found in
common drug products. For example, Pitt found that Sucrets
give a violet coloration for the test. They also tested a
number of common monocyclic resorcinols and icyclic
resorcinols (chromanols) and found them to give a positive
D-L test. Pitt conclud ed that the D-L test is useful as a
“screen” test but not sufficiently selective to be relied upon
for “identification” [17].
Various courts have also found that the marijuana tests
alone or in combination do not prove the presence of
marijuana beyond a reasonable doubt. In 1973, the Supreme
Court of Wisconsin ruled that “standing alone (the D-
L/microscopic exam) is not sufficient to meet the burden of
proving the identity of the substance beyond a reasonable
doubt” [16]. The court also pointed out that even the
prosecution’s expert witness, Michael Rehburg, testified
“that neither of these tests was specific for marijuana. . . . It
is without dispute in this record that functional group tests
used by Rehburg . . . are not exclusive or specific for
marijuana” [17].
In 1979, a trial judge in North Carolina blocked the
conviction of C. Richard Tate by the use of the D-L test. The
trial judge found that the D-L test was “not specific for
marijuana” and had “no scientific acceptance as a reliable
and accurate means of identifying the controlled substance
marijuana” and allowed the defendant to suppress use of the
test results on that basis [18]. This finding was upheld by the
North Carolina Court of Appeals as well as the North
Carolina Supreme Court which found that: “The
determin ation that the test used was not scientifically
acceptable because it was not specific for marijuana was
amply supported by the facts. . . The trial court’s ruling that
the results of the tests conducted on green vegetable matter
by using the Duquenois-Levine color test in the Sirchie drug
kit were inadmissible in evidence was supported by the
court’s findings that the test is not scientifically accepted,
reliable or accurate and that the test is not specific fo r
marijuana because it reportedly also gives a positive reaction
for some brands of coffee and aspirin. . . . The conclusion to
exclude the test results is amply supported by these findings
of fact . . . and the test results were properly suppressed ...”
[19].
In 1979, the U. S. Supreme Court, in Jackson v. Virginia,
found, in effect, that non-specific drug tests that render false
positives such as the D-L, cannot prove the presence of
marijuana, and therefore cannot be the basis for prosecution,
let alone conviction [20].
CONCLUSION
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 [21]. 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.
“. . . It would eviscerate the Jackson standard to sustain
conclusory drug identification in the teeth of the judicially
noticeable fact that every test used to identify the substance
is nonspecific. Even more importantly, sustaining such drug
identifications places a judicial imprimatur on testimony that
cannot justifiably be labeled scientific. The rejection of such
identifications is necessitated not only by due process but
also by the simple demands of intellectual honesty. After
Jackson, sustaining conclusory, nonspecific drug identificat-
ion evidence is both bad science and bad law” [21].
8 The Open Forensic Science Journal, 2012, Volume 5 Kelly et al.
ACKNOWLEDGEMENTS
Research support was provided by the Investigative Fund
from The Nation Institute (JK) and a grant from National
Institute of Justice (OB). We would like to acknowledge the
inspiration of Dr. Frederic Whitehurst.
CONFLICT OF INTEREST
Declared none.
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[4] Ibid., Affidavit, Susan Hart Johns, Bureau of Forensic
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[9] Affidavit of Richard Fox, Lab Director/DEA Mid-Atlantic
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[18] State v. Wind, 60 Wis. 2d 267 (Supreme Court of
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Dakota County Court, Minnesota (1974) file f/4-1-8556;
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#1371173;
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[19] State of North Carolina v. C. Richard Tate, 300 180 N.C. S.E. 2d
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[20] Jackson v. Virginia 443 U.S. 307 (1979).
[21] Imwinkelried, E.J. Jackson v. Virginia: Reopening the pandora’s
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Received: October 12, 2011 Revised: December 27, 2011 Accepted: December 28, 2011
© Kelly et al.; Licensee Bentham Open.
This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecom mons.org/licenses/by-
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