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Why don't cops use breathalyzers more often?

Published in DUI Enforcement Challenges 4 mins read

Cops don't use breathalyzers more often primarily because field breathalyzer tests can yield inconclusive and inaccurate results, making them less reliable as standalone evidence in legal proceedings.

Challenges with Field Breathalyzers

While breathalyzers offer a quick way to estimate a person's Blood Alcohol Content (BAC), their administration in the field presents several challenges that can compromise their accuracy and usefulness as primary evidence:

  • Inconclusive and Inaccurate Results: Portable breathalyzers used by officers on the road are susceptible to various factors that can skew readings. Unlike controlled laboratory environments, the field setting lacks safeguards to ensure precise measurements.
  • Lack of Safeguards: When tests are administered at a traffic stop, there are fewer controls in place compared to a police station or hospital. This can lead to variability in how the test is conducted.
  • Improper Administration: A common issue is the way the individual blows into the machine. If a person does not provide a proper, continuous breath sample, the device may produce a much higher or lower reading than their actual BAC, making the result unreliable.
  • Environmental Factors: Temperature, humidity, and the presence of interfering substances (like mouth alcohol from recent drinking, burping, or certain medical conditions) can also affect the reading.
  • Legal Scrutiny: Due to these accuracy concerns, field breathalyzer results are often easier for defense attorneys to challenge in court compared to more definitive chemical tests like blood draws.

Alternatives and Comprehensive DUI Investigation

Instead of relying solely on a breathalyzer, law enforcement typically employs a multi-faceted approach to gather evidence in a suspected DUI case. This comprehensive strategy strengthens the prosecution's case and includes:

  • Observable Signs of Impairment: Officers note physical signs such as slurred speech, bloodshot eyes, odor of alcohol, unsteady gait, and erratic driving behavior.
  • Field Sobriety Tests (FSTs): These are a series of physical and mental exercises designed to assess a driver's coordination, balance, and ability to follow instructions, indicating potential impairment. Common FSTs include the Walk-and-Turn, One-Leg Stand, and Horizontal Gaze Nystagmus (HGN) tests.
  • Implied Consent Laws: Most states have "implied consent" laws, meaning that by driving on public roads, individuals implicitly agree to chemical testing (breath, blood, or urine) if arrested on suspicion of DUI. Refusal can lead to immediate license suspension.
  • Post-Arrest Chemical Tests: Once a suspect is arrested, they are often transported to a police station or medical facility for more accurate chemical tests, such as:
    • Evidential Breath Tests: These are administered using more sophisticated machines at the police station, often with calibration logs and trained operators, providing more reliable results than field devices.
    • Blood Tests: Considered the most accurate method for determining BAC, as blood samples are analyzed in a laboratory setting under controlled conditions. They can also detect other impairing substances.
    • Urine Tests: Less common for alcohol but can be used to detect the presence of drugs.

The table below summarizes some key challenges associated with relying heavily on field breathalyzers:

Challenge Description
Accuracy Concerns Field tests can yield inconclusive or inaccurate results due to environmental factors or user error.
Lack of Safeguards On-site administration lacks the controlled environment of a lab, reducing accuracy assurances.
Improper Administration Suspects may not blow into the device correctly, potentially leading to inflated or skewed readings.
Legal Admissibility Results can be more easily challenged in court compared to lab-verified blood tests, weakening the case.

While breathalyzers are a valuable tool for initial assessment and probable cause, police often prioritize a combination of observable evidence, field sobriety tests, and more accurate chemical tests post-arrest to build a strong, legally defensible DUI case.

DUI Evidence & Testing