False Results for Drunk Driving Tests Disadvantage DUI Defendants


During DUI cases, prosecuting attorneys tend to present scientific evidence like blood alcohol concentration test results as infallible. However, reports that a California laboratory produced inaccurate test results in several drunken driving cases demonstrate that scientific procedures and machinery are not always as reliable as criminal justice officials present them to be.


Machine Malfunction Produces False Results, Harms Defendants

According to one Southern California news outlet, an Orange County crime laboratory produced defective test results for several months after technicians incorrectly calibrated a blood analysis device.
The machine, which examines the alcohol concentration of blood samples taken from motorists suspected of DUI, produced data that was skewed by approximately .003 percentage points—an amount significant enough to push the blood alcohol content of roughly 20 samples over the legal .08 threshold of intoxication. This means that about 20 DUI defendants may have been wrongly prosecuted and/or convicted of DUI because of flawed evidence.

Drunk Driving Tests can be Unreliable in DUI Cases

This is not the only instance of DUI test results unfairly harming defendants. In fact, ordinary breath testing machines cannot always be trusted to produce reliable results in DUI cases.
There are many factors that affect the accuracy and reliability of breath alcohol concentration (BrAC) assessments including:

  • Mouth and breath temperature
  • Core body temperature
  • Test-taking method, e.g., how long the test taker blows into the machine
  • Machine calibration
  • Alcohol contamination

Test Administrators Must Take Alcohol Contamination into Consideration

Substances like alcohol-based mouthwashes can affect the accuracy of BrAC tests. If a motorist burps, regurgitates, or vomits before completing a BrAC analysis, a breath testing device may also produce skewed results. Therefore, most consider it a best practice to implement a test taker observation period before conducting a BrAC evaluation.

Typically, these waiting periods are 15 to 20 minutes long and help to ensure that the test taker does not ingest any alcohol or alcohol-based substances, or complete any actions that may alter evaluation outcomes. However, no method is foolproof. As the Orange County crime laboratory’s inaccurate machine results show, even the most carefully conducted tests can produce inaccurate results that might harm DUI defendants.

 How to Attack Drunk Driving Tests

adtQuestion-by-question and argument-by-argument, Attacking and Defending Drunk Driving Tests explains how to soften resolute juries by picking apart unyielding police reports and bulletproof lab reports. These courtroom-proven strategies are supported with understandable science in a coordinated trial attack that will leave the prosecution wondering how its formerly solid case became so weak.

Attacking and Defending Drunk Driving Tests is a complete strategy, law, science, and forms guide containing tactics and arguments found nowhere else. While it focuses on attacking drunk driving tests, it also takes you step-by-step from discovery and investigation through motion practice to trial.