October, 2013 - Why Urine Drug Testing Should Never be Admitted Into Evidence in OWI/OUID and other Drug-Related Criminal Cases

Drugged driving arrests are up around the Country and this trend is going to intensify and increase in Michigan also. This is partially due to federal dollars going to state training programs, particularly in the area of drug recognition training and the advent of the so-called Drug Recognition Expert or DRE. If you’ve not started seeing DRE’s yet, the likelihood is that you soon will.

You will see a blood test in most cases involving an allegation of drug use as an element of the offense. If for whatever reason blood was not tested, then the urine will be tested using the same gas chromatography-mass spectrometry (GC-MS) utilized for testing blood samples for drugs. Where this testing method is utilized you will have the same defenses as are applicable to any case involving these testing instruments.

In addition to the more common defenses applicable to blood, the nature of urine as a body fluid provides many different defenses not otherwise applicable to a blood test. In thinking this through on a more intuitive level, remember the function urine serves in human physiology. Urine (from Latin Urina, ae, f.) is a typically sterile liquid by-product of the body secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen that require elimination from the bloodstream. These by-products are eventually expelled from the body during urination, the primary method for excreting water-soluble chemicals from the body. These chemicals can be detected and analyzed by urinalysis.1

Scientists have laid out the entire chemical composition of human urine, revealing that more than 3,000 compounds are found in the fluid, and have published it all in an online database. In the study, which took seven years to complete, the researchers found that at least 3,079 compounds can be detected in urine. Seventy-two of these compounds are made by bacteria, while 1,453 come from the body itself. Another 2,282 come from diet, drugs, cosmetics or environmental exposure (some compounds belong to more than one group).2

Because urine is a fluid composed of an used as a medium to dispose of waste, it’s function is entirely different from that of blood, whose primary function is transportation of chemicals into (rather than out of) body tissues. Accordingly, blood is more “real time” than urine, which tends to provide a more historical record of what has happened instead of what is happening within the body.

This historical record as kept by urine is often very deceptive. For this reason, in determining driving impairment, the analyst should interpret urine specimen results with caution.3 Many of the potential defenses to a urine drug test are not addressed here. The practitioner is urged to perform additional research regarding such issues as the need for duplicate testing and the problems that arise with pooling.

This paper addresses, instead, issues that arise due to more general scientific principals such as reliability, precision and accuracy, and specifically to urine testing using methods other than GC-MS such as might be employed in a hospital. In an OWI causing death or serious injury case, practitioners might see urine testing completed before blood is drawn and sent to the state lab for confirmatory testing. In rare instances practitioners will see only a hospital urine test. Typically hospitals will not use GC-MS but instead will utilize a much less accurate testing method called “immunoassay”.

Applicable Legal Standard

In thinking about suppression, it’s always good to review the rules of evidence, and to generally go back to basics. And, now that MRE 702 has been conformed closely to FRE 702, in interpreting the rules of evidence applicable to urine tests the Michigan courts will often look to federal precedent for guidance. Accordingly, it may be expected that Michigan courts will apply standards for the admissibility of scientific evidence and expert testimony that are similar to those applied by the federal courts under Daubert. If anything, the trial court’s gatekeeping responsibility will be given even more emphasis in Michigan courts.4 In Gilbert5 the Michigan Supreme Court stated:

[T]he trial court’s obligation under MRE 702 is even stronger than that contemplated by FRE 702 because Michigan’s rule specifically provides that the court’s determination is a precondition to admissibility.

The original Daubert decision set forth the following basic tests for admissibility of an expert opinion, related to the underlying theory or technique employed by the expert (i.e., the ‘‘principles and methods’’ prong of the new rule requirements set forth above):

  • Has the theory or technique been tested?
  • Has the theory or technique been subjected to peer review and publication?
  • Is there a known potential rate of error?
  • Are there existing standards or controls?

In summary, the teachings of Daubert have now unequivocally arrived in Michigan. Expert testimony in Michigan courts must be limited to that based on reliable principles and methods, reliably applied, and resting upon a sufficient evidentiary basis. The nature of that evidentiary basis is the subject matter of the recent amendment to MRE 703, and also, is the subject matter of this article.

Why Urine Test Results are Unreliable

Science of Urine Testing for Drugs of Abuse


In the United States, urine drug testing has recently become widely used as a deterrent tactic in combating drug abuse: in the military, the criminal justice system, and later in the workplace.6 Test mythologies adopted by these testing programs normally include an immunoassay (preliminary or initial test) followed by confirmatory gas chromatography-mass spectrometry (GC-MS) analysis of the drug tested positive by immunoassay.7

In the workplace (and by comparison, hospital setting as well), test results are initially considered (within the laboratory) presumptively ‘positive’ or ‘negative’ – terms that do not hold the same meanings as commonly defined in the laboratory for scientific measurements.8 Universal administrative cutoff values, rather than scientific and statistical detection limit date established by individual laboratories, are used as the basis for determining whether a specimen is (presumptively) positive or negative (of the preliminary test). Those considered positive are further tested using a GC-MS protocol.9

Testing Techniques, Methodology and Limitations

Controversies continue to exist regarding the value of urine drug testing in the medical setting. The reasons for these include the drugs involved, the sample, the methods utilized to perform the tests, and the level of understanding of the physician using the data, all of which are closely related to the other.10 Commonly used drug tests yield false positive results at least 10 percent, and possibly as much as 30 percent, of the time.11

In the legal community, use of the term “drug” test in reference to urinalysis testing is really a misnomer. Because urine is a “historical” fluid, what is normally being tested for are metabolites, the inactive residue remaining after the body has processed the drug. This means that no urine detection system can measure “whether a drug is present in the blood, nor does it reveal the time or quantity of drug intake.” The most any drug test can accomplish is to give a “positive” result when a metabolite is present in the test subject's urine.12

This positive result may indicate any one of three separate inferences and does not justify the conclusion that the test subject is a drug user. First, the subject may have recently been exposed to a drug, which is possible through passive inhalation. [FN15] Second, the subject may have previously used the drug, although that person is not necessarily presently impaired, and may have used the drug over 30 days previously.

The following is a summary of the analytical methods used by most laboratories to detect the presence of drugs or their metabolites in urine. As discussed in the Gale Encyclopedia of Surgery13

  • Immunoprecipitation. The simplest immunoassay method measures the quantity of precipitate, which forms after the reagent antibody (precipitin) has incubated with the sample and reacted with its respective antigen to form an insoluble aggregate. Immunoprecipitation reactions may be qualitative or quantitative.
  • Particle immunoassays. By linking several antibodies to the particle, the particle is able to bind many antigen molecules simultaneously. This greatly accelerates the speed of the visible reaction. This allows rapid and sensitive detection of antibodies that are markers of such diseases, as infectious mononucleosis and rheumatoid arthritis.
  • Immunonephelometry. The immediate union of antibody and antigen forms immune complexes that are too small to precipitate. However, these complexes will scatter incident light and can be measured using an instrument called a nephelometer. The antigen concentration can be determined within minutes of the reaction.
  • Radioimmunoassay (RIA) is a method employing radioactive isotopes to label either the antigen or antibody. This isotope emits gamma raysare, which are usually measured following removal of unbound (free) radiolabel. The major advantages of RIA, compared with other immunoassays, are higher sensitivity, easy signal detection, and well-established, rapid assays. The major disadvantages are the health and safety risks posed by the use of radiation and the time and expense associated with maintaining a licensed radiation safety and disposal program. For this reason, RIA has been largely replaced in routine clinical laboratory practice by enzyme immunoassay.
  • Enzyme (EIA) immunoassay was developed as an alternative to radioimmunoassay (RIA). These methods use an enzyme to label either the antibody or antigen. The sensitivity of EIA approaches that for RIA, without the danger posed by radioactive isotopes. One of the most widely used EIA methods for detection of infectious diseases is the enzyme-linked immunosorbent assay (ELISA).
  • Fluorescent immunoassay (FIA) refers to immunoassays which utilize a fluorescent label or an enzyme label which acts on the substrate to form a fluorescent product. Fluorescent measurements are inherently more sensitive than colorimetric (spectrophotometric) measurements. Therefore, FIA methods have greater analytical sensitivity than EIA methods, which employ absorbance (optical density) measurement.
  • Chemiluminescent immunoassays utilize a chemiluminescent label. Chemiluminescent molecules produce light when they are excited by chemical energy. These emissions are measured by a light detector. For example, there are a variety of cross-reacting compounds that are widely reported and many are listed in the reagent inserts or documentation provided by the manufacturers.14

The identities of most reported cross reacting compounds are known, while others are not. For example, it has been reported that unknown metabolites of chlorpromazine, bromphenirmine and labetalol caused false positive results.15

Additionally, some of the analytes targeted as indicators of drug abuse may derive from unintended exposure, food consumption or licit medication. For example, it is well known that morphine and codeine may be observed in specimens collected from individuals consuming food items with poppy seeds. Methamphetamine and amphetamine can derive from the use of Vicks nasal inhaler and a substantial number of licit drugs.16

Clinical interpretation of positive amphetamine and methamphetamine results can be challenging because of the structural similarities of other prescription and OTC products, including diet agents, decongestants, and selegiline used in the treatment of Parkinson’s disease.17

Other possible problems arise with nonspecific binding, and the presence of adulterants. Adulterants may actually destroy the targeted drugs, thus creating a false negative, so are of little interest to the court. However, these include such common household products as ammonia, bicarbonate, bleach, Drano, detergents, peroxide, vinegar and Visine.18 Urine immunoassay tests are uniquely susceptible to false positives and negatives. The same cannot be said of a confirmatory GC-MS, which is why such confirmation is critical.

Finally, unintended passive inhalation of marijuana can also result in detection of the metabolites normally monitored to indicate the abuse of this drug.19 The detection of cocaine metabolite has also been attributed to drinking Health Inca Tea, handling of cocaine-containing currency.20 Cocaine is also a topical anesthetic clinically used in certain trauma, dental, ophthalmoscopic, and otolaryngologic procedures.21 A patient’s urine may test positive for the cocaine metabolite, benzoylecgonine, after such a procedure for up to 2 to 3 days.

Of course this multitude of problems with unconfirmed urine immunoassay testing relates to the testing method itself. Other potential problems relate to such things as human error in chain-of-custody, sample handling and/or preparation in the laboratory, issues with the maintenance (or lack thereof) of the subject equipment, issues related to the controls and calibrators used, and finally, issues and problems related to the reporting of the results.


A hospital urine test usually indicates that “unconfirmed screening results must not be used for non-medical purposes,” and this almost requires no elaboration. However, an understanding of the significant limitations posed by a urine drug screen, combined with a recognition and application of the rigorous legal standard, makes clear that the urine drug test results should be suppressed in virtually any criminal case as failing to meet any reasonable standard of scientific certainty.

by Patrick T. Barone

Patrick T. Barone is an adjunct professor at Cooley Law School where he teaches "Drunk Driving Law and Practice." Mr. Barone is also the co-author of two books on DUI-related issues, including Defending Drinking Drivers (James Publishing), a well-known and highly respected multi-volume national legal treatise. He is a frequent lecturer on trial practice and drunk driving defense tactics. He can be contacted on the web at: www.baronedefensefirm.com.


1. http://en.wikipedia.org/wiki/Urine, last checked 10.22.13.
2. http://www.foxnews.com/health/2013/09/06/what-in-urine-3000-chemicals-and-counting, last checked 10.23.2013.
3. Bartell, Imobersteg, Attacking and Defending Drunk Driving Tests, § 13:40, James Publishing (Rev. 1, 9/09).
4. Longhofer, Michigan Adopts Daubert Principles and Evidence-Based Expert Testimony: Revised MRE 702 and 703, Mich. Bar. J., pg. 34 (Oct. 2004).
5. Gilbert v. DaimlerChrysler, 470 Mich. 749 (2004).
6. Huang, Chang and Liao, Encyclopedia of Forensic Sciences, pg. 651 (Academic Press, 2000).
7. Id.
8. Id.
9. Id.
10. Hammett-Stabler, Urine Drug Screening in the Medical Setting, Clinica Chimica Acta, Volume 315, Issues 1–2, January 2002, Pages 125–135.
11. Greenblatt, David J., Urine Drug Testing: What Does it Test?, New England Law Review, 23: 651-666 (1989)
12. Northern Illinois University Law Review, Urinalysis Drug Testing of Employees at Will: The Need for Mandatory Standards, Spring, Summer (1991).
13 Ramsell, Illinois DUI Law and Practice Guide, Chemical Tests for Drugs Other than Alcohol, Chapter 5. Types of DUI Evidence, § 5:110. (March 2013).
14. Id. At 653
15. Id.
16. Id.
17. Gourlay, Urine Drug Testing in Clinical Practice, supra, pg. 13.
18. Id.
19. Id. At 662.
20. Id.
21. Shults TF. The Medical Review Officer Handbook. 8th ed. North Carolina: Quadrangle Research, LLC; 2002