Drug and Alcohol Evidence Rules

DEFINITION: Proper procedures for collecting and handling evidence to ensure its acceptance by a court in criminal proceedings related to the use or possession of drugs or alcohol.

SIGNIFICANCE: To be sure that the drug and alcohol evidence collected and analyzed during an investigation is accepted in court, first responders, investigators, and laboratory technicians must handle and document the evidence in ways that meet the requirements for admissible evidence.

Statutory rules of evidence are laws that help determine what evidence will be accepted by the court. They are designed to produce a fair, orderly, and efficient legal process that results in the determination of the truth. For example, statutory laws prevent the court from accepting hearsay evidence or evidence that may have been tampered with or altered. In 1975, the US Congress established the Federal Rules of Evidence. In addition to federal evidence laws, each US state has its own set of statutes concerning the admissibility of evidence.

Alcohol Evidence

Alcohol is relevant evidence primarily in cases of underage consumption of alcohol and driving under the influence (DUI) of alcohol. The amount of alcohol a person has consumed can be determined through the use of machines that measure breath alcohol (such as the Breathalyzer), urine testing, or blood testing. In cases of alcohol consumption by underage persons, testing must prove only the presence of alcohol in the body, because any amount of alcohol consumption by an underage individual is a violation of the law. In those of legal drinking age, the evidence must show that the amount of alcohol in the bloodstream is above the legal limit.

The most common reason for a officer to make a suspected DUI stop is observation of a pattern of driving consistent with the driver’s being under the influence of alcohol. If the officer then observes behavior consistent with DUI or smells alcohol, the driver may be asked to perform a field sobriety test. This involves actions such as touching the nose, walking on a road line, or reciting the alphabet. Based on the results of the field sobriety test, the individual may be asked to take a preliminary alcohol screening (PAS) test, commonly called a Breathalyzer test. The PAS gives a rough estimate of the amount of alcohol in the bloodstream. If the individual is arrested for DUI, he or she must provide a blood or urine sample. Each establishes a standard procedure for the collection of these samples.

Urine and blood samples are analyzed by the section of the crime laboratory. Although procedures vary from state to state, the statutory laws of evidence require that each sample be labeled with the time, place, and person from which it came; that it be handled in a way that will not allow it to be tampered with or altered; and that a (a written record of who had possession of the sample at all times, how it was stored, and what tests were done on it) is established and maintained.

Drug Evidence

Controlled substances can take the form of liquids, capsules, tablets, powders, plant material, or irregular masses. Unlike alcohol evidence, where testing is done to measure the quantity of alcohol in the blood, drug testing usually requires only identification of the type of drug in the evidence sample. The job of the toxicology laboratory is to use an array of standard chemical tests to identify the drug. Just as with other physical evidence, a chain of custody must be established for the evidence to be accepted in court.

Each jurisdiction establishes its own procedure for handling different types of drugs. If a large quantity of a drug is seized, only a small sample is taken, following an established sampling protocol, and sent for analysis. When a person is suspected of being under the influence of drugs, the laboratory determines what drug or its metabolites (breakdown products) are present in the individual’s blood or urine. The quantity of illicit drug consumed is usually irrelevant. A standard six-drug panel screens for benzodiazepines, cocaine, marijuana, methamphetamine, opiates, and (PCP). The laboratory techniques used in drug analysis include gas chromatography, mass spectrometry, and immunoassay.

Investigators can request screening for drugs outside those detected by the six-drug panel. Prescription and so-called designer drugs may be difficult to identify, and extensive testing may be required to establish their presence. When a prescription drug is found in the blood, the quantity of drug is also measured and compared with the therapeutic medicinal dose. So long as the chain of custody is maintained, cross-contamination and tampering are prevented, and good records are kept of the tests performed, blood and urine samples generally meet the requirements for statutory submission of physical evidence.

Bibliography

Best, Arthur. Evidence: Examples and Explanations. 6th ed. New York: Aspen, 2007.

Graham, Michael H. Federal Rules of Evidence in a Nutshell. 7th ed. St. Paul, Minn.: West, 2007.

Hawthorne, Mark R. First Unit Responder: A Guide to Physical Evidence Collection for Patrol Officers. Boca Raton, Fla.: CRC Press, 1999.

"Law 101: Legal Guide for the Forensic Expert." National Institute of Justice (NIJ), 7 Aug. 2023, nij.ojp.gov/nij-hosted-online-training-courses/law-101-legal-guide-forensic-expert/pretrial/pretrial-rules-evidence. Accessed 14 Aug. 2024.

Mieczkowski, Tom, and Kim Lersch. “Drug Testing in Criminal Justice: An Historic Overview.” NIJ Journal 243 (1998): 9-15.

Saferstein, Richard. Criminalistics: An Introduction to forensic Science. 9th ed. Upper Saddle River, N.J.: Pearson Prentice Hall, 2007.