Reliability of DUI Breathalyzer in DUI Prosecution

June 2, 2014

DUI Breathalyzer

A history of DUI Breathalyzer device, commonly used by law enforcement to prosecute DUI cases in Los Angeles, can be traced to early 1900s, when it was first noted that alcohol level on breath of impaired individuals is correlated to the alcohol level in blood. The ratio of correlation is now assumed to be a constant and equivalent to 2,100. However, the science development in recent years put into question the reliability of DUI breathalyzer because the correlation of blood alcohol level to breath alcohol level is not constant between different individuals and it also can vary in same person from day to day or hour to hour.

Since the first DUI breathalyzer was used by law enforcement in 1938 in Indiana (at the time it was called a drunkometer), the reliability of DUI breathalyzer was questioned by drunk driving defense attorneys.

For example, the studies that led to adoption of first DUI breathalyzer were done on dogs and not humans (a species that has very different physiology) using rapid delivery mechanisms to the body instead of natural passages (drink that is ingested through mouth).

Despite the recent development in science, California DUI prosecutors still operate on an assumption that the concentration of alcohol in blood remains constant at 2,100 more then concentration of alcohol in breath. This ratio is referred to as “partition ratio”, a subject of number of litigation of recent years. However, an actual ratio of breath alcohol concentration to blood alcohol concentration varies widely (some studies put it as low as 900:1 and as high as 3700:1). The assumption of 2100:1 equates all human blood to the air above it (an unreal assumption as we know that bloods have different qualities in terms of viscosity, hematocrit content etc). Even to a non-scientist it must be obvious that human blood changes depending on diet, levels of dehydration, etc. Moreover, women have less water portion of blood then man, which causes different breathalyzer results – so that woman and man who have the same blood alcohol level will show different results on a breathalyzer. But our legislature is bind to science!

Humidity, air temperature and quality of lung tissue will also affect ratios between breath alcohol level and blood alcohol level.

If you are being tested by DUI breathalyzer after being arrested for a DUI in Los Angeles, and it is a warm summer day, the warm air will cause increased evaporation of alcohol, which in turn will cause an increase of alcohol levels in your breath.

DUI attorney in Los Angeles can help you fight such a case by explaining to the prosecutor judge or jury the effects the external factors or gender have on the breath alcohol level (BrAC) (conversely, cold air will cause condensation of alcohol and lower breath alcohol levels).
Drunk Driving Attorney in our firm are always ready to answer your questions and structure a defense to defense your DUI in Los Angles or near our second office in Van Nuys DUI court.
Please call us (818) 921 7744 for a free consultation.

 

 

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