Intoxilyzer 5000Manufactured by CMI Inc. of Owensboro, KY, the Intoxilyzer 5000 is a infrared spectrometry breath alcohol measurement tool used by law enforcement to determine the Blood Alcohol Level (BAL) of individuals suspected of Driving While Intoxicated (DWI). The Intoxilyzer 5000 works by measuring alcohol content in the breath in parts per million. Under a theory known as Henry’s Law, the Intoxilyzer 5000 assumes a breath to blood ratio of 2,100 parts breath to 1 part blood. Therefore, by measuring the alcohol content in the breath, the Intoxilyzer 5000 extrapolates the estimated Blood Alcohol Content (BAC).

While many states rely on the Intoxilyzer 5000, they are by no means infallible or completely accurate. In fact, in November of 2005, a Florida court ruling disallowed use of the device when the manufacturer, CMI Inc., refused to give defense attorneys exact information and details about how the device computes Breath Alcohol Content.

In addition, scientific studies have been conducted which uncovered very troubling information about the accuracy of the Intoxilyzer 5000 device. In a study entitled ”Variables Affecting Accuracy Precision of Breath Alcohol Instruments including Intoxilyzer 5000” (Rose & Furton), a medical doctor and professor specializing in Medical Forensics at Florida International University revealed several serious factors which can cause Intoxilyzer 5000 to give incorrect readings.

First, they attacked the theory of Henry’s Law and the 2100:1 ratio by stating “In order to understand the application of this Law, one needs to imagine a capped bottle containing water and a little ethanol. The bottle will contain the water and ethanol in two forms; liquid, and gas above the liquid. This law states that at equilibrium, one can measure the concentration of the ethanol in the gas phase, and from that measurement predict the concentration in the simultaneous liquid phase. The comparison being made is that the lungs are like the bottle, the blood in the lungs are like the liquid in the bottle, and the breath is like the gas phase above the liquid. Unfortunately, Henry’s Law does not apply in the lungs.”

The study further indicates that since the exact conditions required to accurately create Henry’s Law do not exist in theIntoxilyzer 5000, the ratio that is used to calculate intoxication (2100:1) is highly susceptible to false positives (indications that the subject’s Blood Alcohol Level is substantially higher than it actually is).

The same study found that are many additional factors including individual rate of metabolism of ethanol (alcohol), breathing, body and breath temperature, and presence of other compounds cannot be accounted for by the Intoxilyzer 5000 and only further increase the propensity for error.

While the Intoxilyzer 5000 may be the “Gold Standard” for law enforcement, it is by no means absolute or incontrovertible evidence that a subject was intoxicated.

Rose S. Furton KG. “Variables Affecting Accuracy Precision of Breath Alcohol Instruments including Intoxilyzer 5000” July 7, 2003, (1-12)