Drug Test Results
By Anne ImObersteg
Edited by Peg Healy
Issues surrounding drug use and abuse arise for clients in almost all fields of legal practice: criminal law, family law, insurance law, employment law, personal injury, workers compensation-even lawyer discipline. When faced with a drug issue, a lawyer must select an appropriate expert, request appropriate discovery, and get a quick education on drugs and drug testing to help the lawyer do effective expert examination and cross-examination.
Choosing an Expert
An expert witness's role is to provide unbiased and accurate information in a manner understandable to a jury. Sometimes information can be elicited from opposing counsel's witness, so calling your own expert at trial may not be necessary. However, if the opposition does call an expert, a qualified forensic toxicologist should perform an independent review of the data on which the opposition expert relies. The toxicologist can critically evaluate the data, procedures, and records to ensure that a drug test result is supported by the analytical data and to interpret the test result.
When selecting an expert, always ask for a résumé and determine if the expert's qualifications are adequate for your purpose. Look for: (1) experience in a crime lab or clinical lab performing the analyses in question; (2) education that directly relates to the issue in question (college-level toxicology classes, or training in ascertaining drug influence); (3) membership in relevant professional organizations; (4) the number of times the expert has been qualified in court, and in which field; (5) experience using the analytical instruments involved in the analyses, interpreting the results, and training others; and (6) seminars attended or hosted, presentations given, publications in a peer-reviewed journal, and special qualifications or honors. Finally, evaluate whether your expert can express an opinion that is easily understood by the jury. Knowledge is useless if it cannot be effectively communicated.
The more information an expert has, the more impartial and accurate the opinion will be. The types of materials to discover will depend on the type of case. Most alcohol analyses of biological specimens (other than breath) are typically performed in duplicate on a gas chromatograph (GC). Drug cases are typically performed in two stages: a presumptive test, followed by a confirmatory test on a gas chromatograph/mass spectrometer (GC/MS).
For blood-alcohol cases, the following records should be requested: (1) a "run list," which shows the order in which your case was analyzed; (2) printed out chromatograms and results of standards and controls; (3) chromatograms of the two results of your case, before averaging and truncation; (4) maintenance and repair logs of the instrument used, three months before and after the chemical test; (5) logs regarding any re-analysis of the sample; (6) proof that the analyst was certified according to state regulations; and (7) the results of the most recent independently administered proficiency test taken by the analyst.
For drug-test cases, request: (1) all screening-test results for the subject's specimen; (2) a description of quality controls and calibration results for the run in which the specimen was tested; (3) identification of the manufacturer of the reagent kit used in the analysis; (4) the manufacturer's product insert provided with the kit; (5) a description of the method used by the laboratory in the analysis, including procedures that differ from the manufacturer's recommendation; (6) the results of specificity testing performed by the lab for the drug in question, specifying the method used; (7) GC/MS data, including chromatograms, relating to the subject's specimen; (8) GC/MS data, including chromatograms, of the calibrators and controls on the subject's specimen run; (9) the GC/MS method identifying the chromatography acceptance criteria, and the composition of the calibrators and controls; (10) the extraction procedure and sample preparation, including the deriving agent used; and (11) the results of recent independently administered proficiency tests given to the analyst.
Making Sense of the Instruments
Drug testing is usually performed in two stages: presumptive and confirmatory. Presumptive tests separate out the negative specimens from those that may be positive for a particular drug class. However, not all positive results mean that the specimen contains the targeted drug. Lack of specificity is a common problem with presumptive immunoassay tests. For example, an immunoassay test for opiates will flag positive for codeine, morphine, heroin, hydrocodone, and hydromorphone. Thus a presumptive positive result for opiates may only mean that an individual has taken Tylenol with codeine or Vicodin for pain relief. On occasion, a random false positive will occur, flagging a sample as positive when there is no drug present.
There are various types of immunoassay techniques on the market. Some common technologies are radioimmunoassay (RIA) or enzyme immunoassay (EIA). Though some immunoassay techniques are more specific to the targeted drug than others, all immunoassay techniques rely on an antibody-antigen relationship to identify a drug class in a sample. Commercial immunoassay kits contain a substrate with an antibody to both a specific class of drugs and also a measured quantity of the targeted drug, which is "labeled" with a tracer such as an enzyme or radioactive isotope. The labeled drug competes with any drug found in the subject's sample for a limited supply of antibodies, so the activity of the tracer is modified in inverse proportion to the quantity of drugs in the sample. A low quantity of "free" drugs in the sample leaves more antibodies to combine with the labeled drug. Positive results must be confirmed by a GC, GC/MS, or equivalent instrument.
The GC separates out the components (drugs) of a mixture. An extract of the specimen is injected into a metal or glass column inside the instrument. The column contains chemicals that slow the migration of some of the compounds while other compounds travel quickly through the column. The analyst compares the time a drug takes to exit the column (called retention time) with that of the retention times of known drugs to determine what is contained in the subject's specimen.
If the analysis is for drugs other than alcohol, the analyst will typically use a GC/MS. When the drug exits the GC, the MS bombards the drug with electrons and shatters the molecule into large and small pieces (ions), depending on the weak points in the drug's structure. The size and quantity of the pieces form a "fingerprint" of the drug. Looking at all the ions and their relative size (called a total ion chromatogram), the analyst can identify the drug in the sample. To determine "quantitation" (how much of the drug is present), a laboratory will perform selected ion monitoring (SIM). Two or three ions of the molecule are chosen to represent the identification rather than the entire molecule. That may decrease the reliability of the instrument, since there is always a possibility that another drug may have the same few ions and be misidentified.
Interpreting the Results
Drugs can be detected in various biological matrices, including hair, saliva, sweat, urine, and blood. If the legal question is whether the subject had ever used or been exposed to the substance, finding the answer is relatively easy. If the question is whether the subject was under the influence of a drug at a particular time, the issue is much more complex. Drugs can be found in a biological fluid long after the desired effects are exhausted. For example, methamphetamine effects may persist for approximately 4 to 6 hours, yet the drug can be found in the blood or urine from 24 to 72 hours and in hair for months. Thus, the first issue in interpretation of results involves the actual ability of the specimen to pinpoint use.
Hair testing has enjoyed some popularity in a variety of arenas: family law, insurance cases, child-custody cases, preemployment, law enforcement, and the military. Unlike urine or blood, hair represents a more lengthy record of drug exposure. Since the average rate of growth for hair is about 1 centimeter (0.4 inches) a month, a hair-test analysis will be performed on a 2-inch length of hair to represent drug use over several months. Segmenting the hair by months is usually not performed.
Hair-test results are more difficult to interpret because not all individuals grow hair at the same rate, and not all hair on one person's head is in the same growth cycle. The presence of a drug in hair therefore cannot support a finding of drug influence. It is merely a record of potential use over a prolonged period of time, which is much longer than the action of the drug. Presence in the hair may not even mean active use of the drug. Drugs can become incorporated into hair from three major sources: blood supply, sweat, and environmental exposure to the drug (e.g., in the form of smoke or dust). In addition, distribution and retention of drugs in the hair can depend on the hair color, the subject's ethnicity, and chemical treatments that affected the hair's porosity.
Saliva testing is simple to perform and the easiest noninvasive method available. Saliva can often be reliably correlated to a blood level. However, for some drugs, circumstances may affect concentration of drugs in the saliva. For example, cocaine concentration in saliva may increase by a multiple of twelve if the saliva pH changes from 6.5 to 7.6.
Sweat is a body fluid that has only recently been fully used in the drug-testing arena. Small amounts of a drug are excreted in sweat. A collection device, such as a patch, is left on the skin of the subject for about a week. At removal, the patch is placed in a vial with a liquid buffer to extract the drug from the patch. The benefits of sweat testing include the noninvasive nature of the procedure and the ability to detect and monitor drug use over a prolonged period of time. These benefits have made the device popular in the drug-treatment field, custody cases, probation, parole, and in the social service arena.
However, there are also drawbacks to the analysis of sweat. The drug concentration in the sweat patch are expressed as nanogram per milliliter (ng/mL) of the buffer liquid used to soak the sweat patch after removal, not as the drug's concentration in the body. Since the patch is left on the skin for approximately a week, it is difficult to tell when during the week the drug was used. In addition, there can be questions of external contamination of the patch, during either the wearing or application and removal.
Blood specimens have the advantage of being able to reflect the type and amount of drug that is circulating in the body at the time of the blood draw. Thus, a blood specimen, as compared to other matrices, may be the most useful to evaluate influence and determine whether it is a therapeutic or an abusive concentration. Issues to consider in blood testing include the necessity of converting a plasma result to a whole-blood result (most often encountered in hospital alcohol testing), the possibility of an inadequate preservation of the blood, and the false assumption that presence of a drug in the blood automatically equates to influence or performance impairment.
Urine is normally suitable to determine use during the past 72 hours. However, some drugs, such as the cannabinoids (marijuana), can be detected for a much longer time (more than 30 days). One major benefit to urine testing is that drug concentration in urine is 10 to 100 times more concentrated than in the blood, making detection easier using conventional drug-testing instruments. However, since urine is collected in the bladder over a period of several hours, a urine sample cannot determine if the donor was under the influence at the time of collection, nor can there be a correlation between urine concentrations and blood concentrations.
The mere presence of a substance in the biological specimen is not enough to determine drug influence, since a drug may be present in the body long after the effects have dissipated. In addition, the substance found must actually cause some effect. Finding a nonactive metabolite or by-product of a drug in the specimen only supports a finding of use, not of influence on performance. Not only must the active substance be found in the body, there must also be a comprehensive and consistent collection of medical information that indicates the substance is having an effect on the body. In criminal law, this is generally achieved via the well-recognized twelve-step Drug Evaluation and Classification (DEC) program, which is a protocol followed by a drug recognition expert (DRE) in a physical examination of the subject. (A certified DRE is typically a police officer who has completed an extensive training program.) When no DRE exam is performed, as in the case of accidents or extensive physical injury, evidence can be gathered from emergency medical records.
Ideally, the DRE observes and documents five general areas that can indicate drug use: vital signs (pulse, temperature, and blood pressure), psychophysical response (coordination), eye signs (nystagmus, eye convergence, and pupil size under several lighting conditions), signs of administration of drugs (e.g., injection sites), and physical and behavioral characteristics (e.g., hyperactivity). The DRE systematically follows a series of steps to determine whether the signs and symptoms observed are consistent with any of the seven categories of drugs evaluated. The results are usually documented on a preprinted Drug Influence Evaluation form, which is usually submitted with the police report.
Field tests are an inherently unreliable method for determining influence, because the normal performance baseline of the subject is unknown. Unless the subject's sober performance under similar circumstances is known, an alleged failure in a field test cannot be associated with drug use. Other difficulties in interpretation include: mistaking correlation for causation, inability to pinpoint the use of a particular drug, a display of symptoms inconsistent with a particular drug, mistaking normal body reactions (fear or excitement) as drug influence, and lack of strict adherence to the twelve-step protocol.
Finally, the mere presence of symptoms or effects consistent with a particular drug does not necessarily mean that the subject is legally under the influence or is experiencing a detriment to performance. For many drugs, scientific studies exploring the impact of the drug on performance, such as driving skills, are virtually nonexistent, or there is no scientific consensus on actual performance impairment. A forensic toxicologist would be able to help a lawyer evaluate these arguments and the merits of a case.
If your case involves a drug test, two major issues need to be analyzed: the accuracy of the test result and the determination of actual influence or performance loss. Careful evaluation of the testing procedure, consideration of the type of sample tested, and consideration of physiological effects (determined via a standardized DEC method) are necessary to get the full picture.
Anne ImObersteg, M.S., J.D., of Anne ImObersteg & Associates in San Jose and Discovery Bay (firstname.lastname@example.org) has 21 years of experience as a forensic toxicologist.