Chicago drug convictions may be based on bad evidence
A recent article  in the
Washington Post discussed the practice of the Las Vegas Metropolitan Police Department
and the Nevada criminal justice system of relying on drug field test kits
for evidence of the presence of controlled substances. Another recent
publication  indicates Chicago relies on similar test results.
What is the problem with the drug tests used in Chicago?
In Chicago, as in much of the Nation, law enforcement relies on drug field
test kits to test suspected controlled substances. These are basic “color
tests,” meaning that if you add a substance to the test pouch and
add the appropriate liquids that come with the test pouch, the liquid
will change colors if there is a controlled substance present. The manufacturers
of these tests are quite clear that the presumptive drug field test kits
are a useful screening tool, but they should not be relied on as proof
that the substance is actually a controlled substance. Unfortunately,
law enforcement and prosecutors in Chicago are relying on these test results
to obtain criminal convictions – even though the test results may
be wrong. In Las Vegas, the drug field tests were wrong 33 percent of
The problem with false positives and the need for confirmatory testing
The reason for this inaccuracy is that the drug field test kits are what
is called a “presumptive test,” which
presumes that a given substance is present. However, the only way to know for sure
is to insist on a “confirmatory test,” which
confirms that the substance is, in fact, what it is presumed to be. This sort of
testing should be done in an accredited laboratory by a qualified drug
chemist, not law enforcement officials.
In practical terms, the use of presumptive testing means, for example,
that the cocaine test kit will turn blue if you add cocaine to the test
pouch, but that isn’t the only substance that will turn the cocaine
test blue. In fact, there are over 80 substances
 that are known to give a “positive” test result for cocaine,
including some household cleaners and acne medications.
Other substances that have been identified  as providing false positive
drug test results include:
- Motor oil
- Dr. Bronner’s Magic Soap
- Loose leaf tea
- Chocolate chip cookies
- Tortilla dough
- Billiards chalk
- Breath mints
- Jolly Ranchers
It is for precisely this reason that the manufacturers caution against
relying on the test results as “proof beyond a reasonable doubt”
that a defendant was in possession of an illegal substance.
Why no one should plead guilty without confirmatory testing
As long ago as 1978, the United States Department of Justice has stated
that the results of drug field test kits, “should not be used for
. Unfortunately, many prosecutors and courts continue to rely on the presumptive
test kits as proof of the existence of a controlled substance. Confirmatory
testing is more costly and time consuming; however, wrongfully incarcerating
people who have not committed a crime is more expensive.
Contrary to what you may have seen on television, drug dealers, particularly
undercover officers pretending to be drug dealers, don’t typically
allow their clients to sample the merchandise before they purchase it.
People who may believe they were in possession of a controlled substance
may actually be innocent of the charges. Without a confirmatory drug test,
no one can say with any degree of certainty that the substance actually
is an illegal substance.
It is for this reason that no one should plead guilty to a drug case without
insisting on evidence of confirmatory drug testing. If faced with a criminal
charge, always secure an experienced criminal defense attorney.
R. Tamara de Silva