Breathalyzer testing
Breathalyzer testing is a method used to measure the concentration of ethanol in a person's breath as an indicator of blood alcohol concentration (BAC). These devices are commonly utilized by law enforcement to assess whether drivers are under the influence of alcohol, often leading to arrests in impaired driving cases. Breathalyzers offer a minimally invasive alternative to blood tests, providing immediate results that can be used as legal evidence when properly calibrated and documented.
The testing process involves the individual blowing into the device, which analyzes the breath sample through various technologies, including chemical reactions or infrared absorption. The accuracy of these devices can vary based on their design and susceptibility to other compounds that may interfere with alcohol detection. Factors such as recent alcohol consumption, smoking, and the use of alcohol-based products can affect test results.
Additionally, understanding the relationship between breath alcohol concentration (BrAC) and BAC is crucial, as they are correlated through a fixed blood/breath ratio. Despite the effectiveness of Breathalyzer tests, legal and physiological debates about their accuracy persist, highlighting the importance of proper administration and attentiveness during the testing process.
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Breathalyzer testing
Definition: Device used to measure ethanol in the breath of a subject as an indication of blood alcohol concentration. Breathalyzer is also the trade name of a series of instruments designed to analyze breath alcohol.
Significance: Police officers commonly conduct analyses of the breath of drivers suspected of driving under the influence of alcohol, and Breathalyzer results are often used as grounds for arrest in cases of impaired driving. Such analyses are increasingly used also in workplace drug-testing and research applications. The accuracy and precision of the measurements produced by Breathalyzer testing, which are related to physiological and instrumental variables, are often debated in court.
Police officers often ask drivers whom they suspect are under the influence of alcohol to provide samples of their breath by blowing into instruments—at the roadside or at police detachments—that can determine the concentration of alcohol in their breath. Such breath analysis is valuable because the sample collection is minimally invasive, especially in comparison with direct analysis of blood. Breath samples are analyzed upon collection, which establishes sample continuity. When the results are properly documented, and when the instrument is properly calibrated and in good working order, the measurements are typically used as evidence in court.
The instruments used in breath alcohol analysis are based on a variety of designs. The Breathalyzer 900/900A uses oxidation of ethyl alcohol (ethanol) in a fixed volume of breath by potassium dichromate in a standard solution to cause a shift in the solution absorbance spectrum (that is, a color change); the change in absorbance is correlated with the alcohol concentration in the breath sample. Newer instrument designs typically rely on ethanol detection based on absorbance of infrared radiation at selected wavelengths or on electrochemical reaction of the ethanol in the breath sample. Some instruments are portable, and small, handheld units are often used as screening devices; that is, law-enforcement personnel use them to determine whether alcohol is present in subjects within a concentration range that warrants further evidentiary breath testing. Different designs often vary in terms of accuracy and in their susceptibility to other interfering compounds in the breath.
Breath alcohol concentration (BrAC) is correlated with blood alcohol concentration (BAC). Henry’s law states that, at a given temperature, the ratio of the concentration of a volatile substance in solution to that of the substance in the vapor above the solution is fixed. Physiologically, such a system exists in the capillaries within the alveoli (air sacs) of the lungs. Volatile compounds, including alcohol, are exchanged between the alveolar air and the blood within these capillaries. BAC is thus determined by multiplication of the measured BrAC by this ratio, termed the blood/breath ratio (BBR). Reported BBR averages typically fall within the range 2,200–2,500.
To be detected in the breath, a compound must be sufficiently volatile, present at sufficient blood concentrations, and measurable by the detection scheme of the instrument. To characterize potential interferences, the response of evidentiary instruments to volatile compounds (such as acetone, isopropanol, methanol, and toluene) should be measured in vitro at toxicologically relevant fluid concentrations (that is, those associated with occupational or environmental exposure, a disease state such as diabetes mellitus, or nonfatal substance abuse). The influence of such compounds on BrAC measurements depends on their chemical properties and the detection scheme of the instrument. Further safeguards against falsely elevated results are provided by careful observation of the subject by the test administrator and by the collection of a detailed history of the subject being tested.
Bibliography
Clark, Paul A. "Do Warrantless Breathalyzer Tests Violate the Fourth Amendment?" New Mexico Law Review 44.1 (2014): 89. Print.
Garriott, James C., ed. Medical-Legal Aspects of Alcohol. 4th ed. Tucson, Ariz.: Lawyers & Judges Publishing, 2003.
Karch, Steven B., ed. Forensic Issues in Alcohol Testing. Boca Raton, Fla.: CRC Press, 2007.
Levine, Barry, ed. Principles of Forensic Toxicology. 2d ed., rev. Washington, D.C.: American Association for Clinical Chemistry, 2006.
Tuorto, Stephanie R. "You Blew It: The Confrontation Clause & Breathalyzers as Testimonial Evidence: People v. Umpierre." Touro Law Review 4 (2014). Print.