DUI Pro Simulator

Dubowski’s Principles in Alcohol Testing

Dr. Kurt M. Dubowski is a renowned forensic toxicologist whose work has greatly influenced DUI alcohol testing procedures and interpretation. DUI attorneys often encounter Dubowski’s principles in two main areas: (1) the proper administration of alcohol tests (ensuring accuracy and reliability), and (2) the scientific values used in alcohol metabolism calculations. Understanding these principles helps defense lawyers evaluate the strength of the prosecution’s evidence and identify potential weaknesses in testing or assumptions.

Quality Control in Breath Testing

One of Dubowski’s significant contributions was establishing strict quality assurance safeguards for breath alcohol testing. He emphasized that adherence to standardized procedures is essential to produce reliable, court-admissible results. Key Dubowski guidelines for breath tests include:

  • Pre-test observation period: A 15–20 minute deprivation/observation period before the test to ensure the subject hasn’t ingested alcohol or regurgitated (which could skew results). This helps ensure any mouth alcohol has dissipated and the sample is truly representative of deep lung air.
  • Blank test: Running a blank test (zero check) immediately before collecting each breath sample. The testing device should show 0.000% to confirm no residual alcohol from prior tests or any contamination is present.
  • Duplicate samples: Collecting and analyzing at least two separate consecutive breath samples. The results should be within a close range of each other (often within 0.02% BAC) to verify consistency. Significant differences between two blows may indicate an unreliable test or instrument issue.
  • External control tests: Using a control sample of known alcohol concentration during the testing sequence. A control test (e.g., a simulator solution or dry gas standard at a known value like 0.08%) ensures the instrument is correctly calibrated at the time of the subject’s test. The device’s reading for the control should match the expected value within a tight tolerance.

These safeguards, championed by Dubowski and others, are now standard practice in many jurisdictions. A DUI defense attorney will check whether law enforcement followed such steps. If any of these protocols were skipped or done improperly, it can raise doubt about the breath test’s accuracy.

Scientific Values: Distribution and Elimination

Dubowski also conducted foundational research on how alcohol is distributed and eliminated in the human body – data that underpins many BAC calculations. Two critical concepts are the alcohol distribution ratio (Widmark “r” value) and the alcohol elimination rate:

  • Widmark "r" values: These represent the fraction of body weight that is water (where alcohol distributes). Widmark’s original studies suggested average r values of about 0.68 for men and 0.55 for women. Dubowski’s research refined this, finding averages around 0.73 for males and 0.66 for females. Importantly, there is variability: in Dubowski’s data, one standard deviation was approximately ±0.067 for men and ±0.082 for women, which means roughly two-thirds of men fell between about 0.66 and 0.80, and two-thirds of women between about 0.58 and 0.74. Expanding to a wider population (95% interval) implies an even broader range (approximately 0.60–0.86 in men, 0.50–0.82 in women). In practical terms, not everyone fits the “average” – a lean, muscular individual might have a higher effective distribution volume (thus a lower BAC per drink), while an individual with higher body fat might have a lower distribution volume (higher BAC per drink).
  • Elimination rate: Dubowski and others confirmed that an average person eliminates alcohol at around 0.015% BAC per hour. However, studies have shown significant variation here as well. In one 1985 study, elimination rates among individuals ranged from about 0.006% up to 0.028% per hour. Additionally, drinking habits can influence this – a non-habitual drinker might eliminate on the lower end of the spectrum (~0.010–0.012%/hr), whereas a chronic heavy drinker could eliminate faster (sometimes on the order of 0.020–0.025%/hr or more). Forensic calculations (and tools like DUIPro) often use 0.015%/hr as a default, but a savvy defense will highlight that real-world elimination rates differ person to person.

In summary, Dubowski’s principles remind us that accurate DUI analysis rests on both proper testing procedures and sound scientific assumptions. For defense attorneys, invoking Dubowski is a way to stress adherence to best practices (e.g., was the breath test conducted by the book?) and to acknowledge human variability in alcohol metabolism (e.g., is the State’s BAC extrapolation assuming averages that might not apply to the defendant?). By understanding and leveraging these principles, attorneys can more effectively challenge evidence or present alternative interpretations in DUI cases.