Defending a Drug DUI – Toxicology

DUI and Drug Toxicology

If your DUI arrest involves drug use the criminal lawyer you choose to represent you can make a huge difference. In order to properly investigate your DUI, your attorney should know the differences between the toxicology involved with driving under the influence of alcohol versus driving under the influence of drugs. Please contact our Southern California DUI lawyer to learn more about the drug toxicology involved in your DUI case or review the excerpt below published by the NDAA:

The duration and the intensity of a given drug’s effects depend on the dose administered, individual metabolism, frequency of drug use and the presence of other drugs. Because many of these factors are unknown, toxicological interpretation is often difficult. Questions regarding administration time can sometimes be answered using the pharmacokinetic principles, such as drug half-life. For a drug that is eliminated by first order kinetics, 99% of the drug is eliminated by seven half-lives, with less than 1% remaining in the body. By ten half-lives, 99.9% has been eliminated. Although detection times for different drugs can be estimated, these vary with dose, method of analysis and metabolic factors. Although the con- centration of a particular drug in a blood sample provides important information, it should be considered in conjunction with reports of driving behavior, physiological signs and other data.

Blood and urine are the most frequently encountered biological fluids in DWI casework. However, DWI statutes in some states make provisions for alternative specimens, for example, saliva. The benefits and weaknesses of blood, urine and saliva samples are described below:

Blood

Advantages:

• A drug that is circulating in the blood may bind to receptors in the brain.

• Less-readily adulterated than urine due to method of collection.

• Quantitative, meaning the amount of drug in the blood may have some 
interpretive value.

• Detection times are much shorter than in urine. Therefore, a blood 
sample that contains a drug is more likely to indicate recent usage compared to a urine sample.

Disadvantages:

• Many drugs have a limited detection window in blood; it may be difficult to collect a sample in a short period of time (transporting individual from scene to collection site, etc.).

• There are complicated statutory regulations or protocols governing who is qualified to collect the sample and how it must be collected, processed and stored.

• Testing of blood is labor intensive and expensive compared to urine.

Urine

Advantages:

• Easily collected.

• Can be screened for drugs more readily (less laboratory time required 
as compared to blood testing).

• Longer detection times for most drugs or metabolites. 


Disadvantages:

• Limited quantitative meaning for most drugs. In the absence of other information, a urinary metabolite reported as “present” may have limited significance when trying to determine whether the individual was impaired.

• More-readily adulterated, therefore requires careful collection procedures to prevent the sample from being compromised (e.g., diluted, replaced or manipulated by use of an additive or “masking agent”).

• Urinary detection times are even more difficult to predict due to differences in fluid intake, diuresis (excessive elimination of urine) and the effect of urinary pH on drug elimination. The relative acidity or alkalinity of the urine can determine how quickly a particular drug is eliminated from the urine. However, urine drug results may be useful in determining an approximate time frame during which drug expo- sure took place. For example, the heroin metabolite 6-acetylmorphine is detectable in urine for approximately 2-8 hours after ingestion.

Saliva

Advantages:

• Easily collected.

• Can be screened for drugs easily.

Disadvantages:

• Some pharmacological interpretation may be possible but there is limited reference data at present.

• Many drugs have limited detection window in saliva.

• Drugs partition into saliva from the blood to varying degrees; the 
degree to which a particular drug is present in saliva depends on many 
variables, including the pH of the saliva.

• Possibility of sample adulteration (by mouth).

• Relatively small volume available for analysis—this may prevent defendant from obtaining “independent test.”


Remember: Because the drug dose usually is unknown, it is generally not possible for a toxicologist to determine exactly when the drug was administered. However, the toxicologist may be able to infer an approximate window of drug use. For example, THC increases very rapidly during marijuana smoking, and upon cessation, is eliminated rapidly from the blood. As a result, elevated levels of THC in blood are a good indication of recent drug use. Cocaine has a short half-life and is relatively unstable. Therefore, the presence of elevated levels of cocaine in a blood sample may also indicate moderately recent use. The meaning of “recent” use will vary from one drug to the next. 
The characterization of certain, specific concentrations of drugs in blood as therapeutic, toxic or lethal is often useful, but must be assigned with caution due to inter-individual differences. These ranges overlap for some drugs, making it difficult to classify the concentration in this way. 


Remember: Human performance may be impaired at therapeutic concentrations.

A therapeutic level of a hypnotic or sedative drug can impair driving due to the central nervous system depressant effects. Even low or sub-clinical concentrations of some drugs in blood are associated with impaired driving. Following chronic use of a stimulant drug like methamphetamine or cocaine, an individual may experience extreme fatigue and exhaustion, consistent with the “crash” phase of drug use, sometimes called the “down- side.” During this time, when an individual is experiencing the negative reinforcing effects, drug concentrations are much lower than during the acute or “high” phase, when positive reinforcing effects predominate. Thus, toxicological interpretation is usually based upon a combination of toxicological analyses, case information, and field observations made by law enforcement personnel or clinicians who may have had contact with the individual.
Defending a Drug DUI – Toxicology

June 23, 2013

DUI and Drug Toxicology

If your DUI arrest involves drug use the criminal lawyer you choose to represent you can make a huge difference. In order to properly investigate your DUI, your attorney should know the differences between the toxicology involved with driving under the influence of alcohol versus driving under the influence of drugs. Please contact a Sarasota DUI lawyer to learn more about the drug toxicology involved in your DUI case or review the excerpt below published by the NDAA:

The duration and the intensity of a given drug’s effects depend on the dose administered, individual metabolism, frequency of drug use and the presence of other drugs. Because many of these factors are unknown, toxicological interpretation is often difficult. Questions regarding administration time can sometimes be answered using the pharmacokinetic principles, such as drug half-life. For a drug that is eliminated by first order kinetics, 99% of the drug is eliminated by seven half-lives, with less than 1% remaining in the body. By ten half-lives, 99.9% has been eliminated. Although detection times for different drugs can be estimated, these vary with dose, method of analysis and metabolic factors. Although the con- centration of a particular drug in a blood sample provides important information, it should be considered in conjunction with reports of driving behavior, physiological signs and other data.

Blood and urine are the most frequently encountered biological fluids in DWI casework. However, DWI statutes in some states make provisions for alternative specimens, for example, saliva. The benefits and weaknesses of blood, urine and saliva samples are described below:

Blood

Advantages:

• A drug that is circulating in the blood may bind to receptors in the brain.

• Less-readily adulterated than urine due to method of collection.

• Quantitative, meaning the amount of drug in the blood may have some 
interpretive value.

• Detection times are much shorter than in urine. Therefore, a blood 
sample that contains a drug is more likely to indicate recent usage compared to a urine sample.

Disadvantages:

• Many drugs have a limited detection window in blood; it may be difficult to collect a sample in a short period of time (transporting individual from scene to collection site, etc.).

• There are complicated statutory regulations or protocols governing who is qualified to collect the sample and how it must be collected, processed and stored.

• Testing of blood is labor intensive and expensive compared to urine.

Urine

Advantages:

• Easily collected.

• Can be screened for drugs more readily (less laboratory time required 
as compared to blood testing).

• Longer detection times for most drugs or metabolites. 


Disadvantages:

• Limited quantitative meaning for most drugs. In the absence of other information, a urinary metabolite reported as “present” may have limited significance when trying to determine whether the individual was impaired.

• More-readily adulterated, therefore requires careful collection procedures to prevent the sample from being compromised (e.g., diluted, replaced or manipulated by use of an additive or “masking agent”).

• Urinary detection times are even more difficult to predict due to differences in fluid intake, diuresis (excessive elimination of urine) and the effect of urinary pH on drug elimination. The relative acidity or alkalinity of the urine can determine how quickly a particular drug is eliminated from the urine. However, urine drug results may be useful in determining an approximate time frame during which drug expo- sure took place. For example, the heroin metabolite 6-acetylmorphine is detectable in urine for approximately 2-8 hours after ingestion.

Saliva

Advantages:

• Easily collected.

• Can be screened for drugs easily.

Disadvantages:

• Some pharmacological interpretation may be possible but there is limited reference data at present.

• Many drugs have limited detection window in saliva.

• Drugs partition into saliva from the blood to varying degrees; the 
degree to which a particular drug is present in saliva depends on many 
variables, including the pH of the saliva.

• Possibility of sample adulteration (by mouth).

• Relatively small volume available for analysis—this may prevent defendant from obtaining “independent test.”


Remember: Because the drug dose usually is unknown, it is generally not possible for a toxicologist to determine exactly when the drug was administered. However, the toxicologist may be able to infer an approximate window of drug use. For example, THC increases very rapidly during marijuana smoking, and upon cessation, is eliminated rapidly from the blood. As a result, elevated levels of THC in blood are a good indication of recent drug use. Cocaine has a short half-life and is relatively unstable. Therefore, the presence of elevated levels of cocaine in a blood sample may also indicate moderately recent use. The meaning of “recent” use will vary from one drug to the next. 
The characterization of certain, specific concentrations of drugs in blood as therapeutic, toxic or lethal is often useful, but must be assigned with caution due to inter-individual differences. These ranges overlap for some drugs, making it difficult to classify the concentration in this way. 


Remember: Human performance may be impaired at therapeutic concentrations.

A therapeutic level of a hypnotic or sedative drug can impair driving due to the central nervous system depressant effects. Even low or sub-clinical concentrations of some drugs in blood are associated with impaired driving. Following chronic use of a stimulant drug like methamphetamine or cocaine, an individual may experience extreme fatigue and exhaustion, consistent with the “crash” phase of drug use, sometimes called the “down- side.” During this time, when an individual is experiencing the negative reinforcing effects, drug concentrations are much lower than during the acute or “high” phase, when positive reinforcing effects predominate. Thus, toxicological interpretation is usually based upon a combination of toxicological analyses, case information, and field observations made by law enforcement personnel or clinicians who may have had contact with the individual.

Multiple drug use can complicate interpretation, so drug combinations need to be examined in terms of their ability to interact with each other and produce additive, synergistic or antagonistic effects:

• Additive effects occur when a combination of drugs produce a total effect that is equal to the sum of the individual effects

• Synergistic effects occur when a combination of drugs produce a total effect that is greater than the sum of the individual effects

• Antagonistic effects occur when the effect of one drug is lessened due to the presence of another drug

A trained toxicologist will be familiar with the types of drugs that can have additive, synergistic or antagonistic effects.

Interpretation of toxicology results is compounded by a number of factors which includes, but is not limited to multiple drug use, history of drug use (chronic vs. naïve user), overall health, metabolism, individual sensitivity, individual response and withdrawal. The same dose of drug given to two individuals may possibly produce similar effects but with varying degrees of severity that elicits a different response. The presence of a drug alone in a person’s blood or urine does not necessarily mean that he or she was impaired. Other information, such as documentation of appearance, behavior, performance on standardized field sobriety tests, DRE evaluation or driving behavior, is also important. Based on a combination of these factors it is often possible for a toxicologist to provide expert testimony regarding the consistency of this information with driving impairment.

TESTING METHODOLOGY IN THE FORENSIC TOXICOLOGY LABORATORY

Most forensic toxicology laboratories that routinely analyze DWI case samples for drugs utilize a two-tiered approach. Initially, samples are screened for common drugs or classes of drugs using an antibody-based test. Samples that screen positive are then re-tested using a second, more rigorous technique, usually called confirmation.

Screening Tests (Presumptive Tests) vs. Confirmatory Tests

Assume for a moment that you have in your hand a key ring with ten keys, all made of brass, all appearing to have the same cut. In front of you is a door with a lock. A few of those will fit in the lock (screening test with false positives since the keys are structurally similar to each other) but only one will actually turn and unlock the door (confirmation test). This holds true for drug testing, as well.

Screening Tests

An immunoassay test is the most common type of screening test for drugs of abuse. Using this type of test, a drug or metabolite in a biological sample can be tentatively identified using an anti-drug antibody. If a drug is present in the sample, the anti-drug antibody will bind to it; if no drug is present in the sample, the anti-drug antibody will not bind to the sample. Various methodologies and detection methods are utilized, giving rise to a number of immunoassays. These include enzyme linked immunosorbent assays (ELISA), enzyme multiplied immunoassay technique (EMIT), fluorescence polarization immunoassay (FPIA), cloned enzyme-donor immunoassay (CEDIA) and radioimmunoassay (RIA).

Immunoassay test results are considered presumptive, not conclusive, because the antibodies that are used may cross-react with other substances to varying degrees, resulting in false positive results. Analogs or substances that are structurally similar to the drug are most likely to produce a false positive. For example, common over-the-counter cold medicines that contain pseudoephedrine may cause a false positive methamphetamine immunoassay result.

Most laboratories utilize screening tests only to determine which drugs or classes of drugs might be indicated. This allows confirmatory tests to be performed for the drugs indicated by the immunoassay. Since it is unfeasible to test every sample for every drug using confirmatory proto- cols, screening tests are used principally to determine where to focus analytical resources in the laboratory.

Cut-offs

The immunoassay test will have a cut-off value or threshold concentration, above which a sample is considered positive. Cut-off concentrations for urinary workplace drug testing are federally mandated by the Substance Abuse and Mental Health Services Administration (SAMHSA). These cut-off concentrations do not apply to forensic testing in DUID casework. The majority of state toxicology laboratories that perform drug tests in criminal casework set cut-off concentrations below the SAMHSA guidelines. This is because workplace drug testing cut-offs in urine are set so that inadvertent drug exposure (e.g. poppy seed ingestion) does not produce a positive drug test. As a result, the cut-offs are elevated so that workers who unintentionally expose themselves to drugs are not penalized. The forensic toxicology laboratory may utilize lower cut-off concentrations for blood samples compared with urine because of reduced detection times and concentrations in blood compared to urine. It is essential for law enforcement personnel to understand the implications of a negative laboratory result in this context.

Confirmatory Tests

The confirmatory test is more specific and usually more sensitive than the initial immunoassay test. The most frequently used confirmatory technique is gas chromatography-mass spectrometry (GC-MS or “GC-Mass Spec”) although others include high performance liquid chromatography (HPLC), liquid-chromatography-mass spectrometry (LC-MS) and others.

TESTING METHODOLOGY IN THE FORENSIC TOXICOLOGY LAB

The increased specificity of the confirmatory technique allows the drug to be qualitatively identified, i.e. the ability to determine specifically which drug is present. For example, GC-MS can be used to distinguish structurally related drugs such as pseudoephedrine from methamphetamine. A quantitative analysis may be performed in blood samples, whereby the concentration of the drug is determined.

Unlike the screening tests described earlier, which are performed with little or no sample preparation, confirmatory drug tests usually require extensive sample preparation or “clean up.” In other words, the drug must be isolated from the biological sample prior to testing on the instrument. This is typically achieved using liquid-liquid extraction or solid phase extraction, whereby drugs in a complex mixture (e.g., blood, urine) are separated from the biological sample. Once the drugs are extracted from the sample, they can then be subjected to confirmatory analysis. For this reason, confirmatory tests are a great deal more labor-intensive than screening tests. Depending on the number of drugs that are present, it may take several days to complete the tests because each drug may require a different extraction and separate confirmatory analysis.

The basis for most confirmatory techniques is separation and positive identification. GC-MS is considered the “gold standard” for methods of confirmatory drug identification. In this method, individual components (drugs and metabolites) are first separated, based upon their chemical and physical properties, by the gas chromatograph (GC). The separated drug(s) then enters the mass spectrometer (MS), where it undergoes molecular fragmentation, resulting in a characteristic mass spectrum or fragmentation pattern. This “molecular fingerprint” of the drug, together with the characteristic retention time from the gas chromatograph allows the drug to be positively identified.

A helpful and widely used analogy for the GC-MS method is the following: inside the GC oven is a long, thin, coiled column; think of this column as a racetrack with different types of vehicles (drugs) traveling around it. Some cars are small and fast (methamphetamine), others big and slow (alprazolam); the road conditions (internal coating of the column) also dictate which cars travel faster—cars with special tires might perform better in the snow, etc. As the cars travel around the track at different speeds they become separated and ultimately each crosses the finish line (the MS detector) and generates a unique “retention time.” At
the finish line, each car is involved in a serious collision and is essentially blown apart by the MS; this generates pieces (molecular fragments) of the car, such as a bumper, hood, headlight, etc. These pieces are then com- pared with other cars of the same make, model and year (drug standards)—which allows for a near perfect overlay of car parts (unique drug fragmentation patterns) and finish times (retention times) for a positive drug identification. The GC-MS identification is based fundamentally upon how drugs are “put together” or arranged chemically, including molecular attractions which ultimately dictates how a molecule or drug will fragment or “blow up.”

CASE PREPARATION AND THE TOXICOLOGIST AS EXPERT WITNESS

Depending upon the evidentiary rules in your jurisdiction, a toxicologist may be necessary to testify at trial to establish the authenticity of the toxicology report, chain of custody and the implication and validity of the test results. Even if such testimony is not necessary to get the evidence admitted, prosecutors must consider carefully the additional benefits of having the toxicologist present to interpret the test results and pro- vide expert testimony. Obviously, manpower concerns and costs associated with expert testimony likely limit the use of a toxicologist, but in some cases, expert testimony from a toxicologist might be essential. This is especially true in DUID cases, where the effects of drug or poly-drug consumption, and the meaning of drug concentrations, are not a matter of common knowledge to the layperson.

It is unlikely that a toxicologist will unequivocally state that all drivers who have a drug or metabolite in their blood or urine are impaired. Determination of impairment requires a case-by-case evaluation, so be sure to obtain the opinion of a toxicologist well before trial. Nothing is worse than having your own witness deliver an unexpected opinion to the jury. Since drug effects are complex, toxicologists may ask many questions before they can arrive at an opinion:

• How was the person driving?
• What was the reason for the traffic stop?
• Was there a crash?
• Was the person injured? What was the nature of the injuries?
• If so, were medications administered at the hospital?
• What is known about the overall health of the individual?
• Were field sobriety tests performed? If yes, what were the results?
• Was a DRE evaluation performed? What were the results?
• What signs, symptoms or behaviors were documented (motor skills, speech patterns, eye movements, etc)?

When the DRE Opinion Differs from the Toxicology Report

In most circumstances, the DRE opinion and the toxicology report agree. But toxicology results that do not agree may need to be addressed by a toxicologist who is familiar with the DRE evaluation process. For example, in the “crash” or “downside” phase of stimulant use, a person experiencing extreme fatigue and exhaustion may appear to be under the influence of a depressant or narcotic drug. Marijuana and stimulants increase blood pressure, increase pulse, and can produce eyelid or body tremors. Stimulants tend to speed up the internal clock and dilate pupils, and marijuana can distort pupil size and the internal clock. These similarities in the known effects of drugs at varying phases of ingestion or elimination can sometimes make it more difficult to identify the class of drug responsible. This is further complicated by poly-drug use, whereby the individual has ingested any number of substances, each of which exhibits certain characteristics on its own, but together these substances likely result in a whole host of contradictory signs and symptoms.

Laboratories cannot test for every known drug. Testing is both labor- intensive and expensive. Each laboratory will likely have a policy for drug testing in DUID cases that may limit the scope of the tests that are performed. Some laboratories may screen samples only for common classes of drugs to the exclusion of other, less common drugs, while other labs may conduct exhaustive toxicology. Be familiar with both testing protocols and policies governing how drug-related DWI casework is handled. Keep in mind as well that as newer drugs are developed a screening and confirmatory test may not yet exist. For these reasons, a negative toxicology report does not conclusively mean no drugs are in the person’s system. It may simply mean that the scope of the testing was too limited, the cutoff was too high, or a test for that particular drug was not available.

Witness Selection

Forensic toxicology can be divided into three main fields: post-mortem toxicology, workplace drug testing and human performance toxicology. Human performance toxicology is concerned with the mental and physical effects of drugs that may impair a person’s ability to safely operate a motor vehicle. This is a challenging field, and an expert witness must be familiar with this sub-discipline.

Because of the breadth and scope of toxicology, it is important to deter- mine that the “expert” has the necessary credentials. For example, a clinical toxicologist who performs drug tests in an emergency room or hospital may not be familiar with the effects of drugs on driving. Likewise, a toxicologist employed in the field of workplace or employee drug testing may not have expertise in human performance toxicology. The following questions may help identify the most appropriate witness for expert testimony (See Appendix for additional questions):

• What type of toxicologist are you?

• Are you familiar with the field of performance toxicology and in particular, the effects of drugs on driving?

• How did you gain this familiarity?

• What specialized training have you received in this area?

• Are you familiar with drug testing methodology and interpretation of the results?

• How many times have you been qualified as an expert witness on the effects of drugs on driving and in what courts?