DUI cases involve scientific evidence of alcohol impairment in the driver facing DUI charges. This evidence comes includes police officer observations of alcohol impairment and some type of measurement of the driver’s blood alcohol level; either through a blood test or breath test. The breath test is done through the use of a breathalyzer, a device of dubious scientific reliability.
There are two general issues that can be used to beat a breathalyzer result and win a DUI case:
1. Attacks on the maintenance, calibration, accuracy and operation of the breathalyzer and
2. Attacks on the validity of the result as a way to measure blood alcohol level.
Maintenance, calibration, accuracy and operation:
At first glance, the information gathered by a breathalyzer would seem daunting to someone facing DUI charges. Breathalyzers have a mysterious, almost authoritative quality about them that people assume they are always accurate and accurate to a high degree. This actually is a good thing for a defense lawyer! Why? Because of the apparent “high degree” of accuracy of the machine, if it is off, even by a small amount, the case against a DUI defendant can quickly turn in the defendant’s favor.
In order to be as “accurate” as depicted, EACH and EVERY protocol, procedure and policy that a law enforcement agency using a breathalyzer has to be followed exactly. A small deviation can render this “highly accurate” measurement invalid.
CALIBRATION: To be accurate to the level demanded by Title 17 (a California law that regulates alcohol measurement in DUI cases) the machine must be calibrated every 10 days or 150 uses. Law enforcement agencies have been known to not calibrate the equipment as often as is required by law. If the agency in your case didn’t calibrate the breath machine they used in your case, this is a defense that can invalidate the breath result.
MAINTENANCE: Because of the highly sensitive nature of the breath testing done, the machine has to be maintained to the standards set forth in Title 17 (see link). This means any error messages, or false readings that are found during normal calibration or during testing itself MUST be corrected in accordance with the standards and protocols in Title 17. If not, the results can be successfully attacked in court.
OPERATION: The improper operation of the breathalyzer machines used in DUI cases is at the same time shockingly common and devastating to a prosecutor’s case. Again, the rules in Title 17 lay out the proper operation and use of a breathalyzer in a DUI case. This includes a 15 minute observation period that police have to observe the driver for signs of burping, vomiting or other regurgitation as they may cause a false high reading as a result of “mouth alcohol.”
VALIDITY AS AWAY TO MEASURE BLOOD ALCOHOL: Using a breath monitoring device as a way to measure BLOOD alcohol level is dubious if you stop and think about it… Why? Because the driver’s Blood alcohol level is the important measurement the police are trying to get and the prosecutor MUST PROVE at trial. Yet, breathalyzers measure a person’s breath and the alcohol it contains. The use of something called “partition ratio” is used by law enforcement to quantify the person’s blood alcohol level when measuring a person’s breath in a breathalyzer. This partition ratio uses a formula that a law enforcement scientist (called a criminalist) uses to extrapolate value for the blood sample. The measurement that is arrived at is based on the use of a “standard” value for everyone: old, young, fat, skinny, female, male on and on, to extrapolate the level of blood alcohol from a breath test. This is absurd because the amount of alcohol in a person’s breath varies based on the characteristics of their lungs, the lining of the lungs, and other unique metabolic traits that each person has. Simply put, the use of breath measuring for blood sampling is not as accurate as people are led to believe.
A DUI law firm with attorneys that regularly deal with DUI cases can explain how and other defenses win DUI cases. Its important to understand breathalyzers and their strengths and weaknesses if you or someone you know is facing a DUI.