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Breathalyzer Accuracy

The state of Rhode Island requires all operators to submit to a chemical analysis if suspected of DUI. There are various types of chemical testing including; breath, blood and urine testing. Refusal to submit to such testing will generally result in a loss of license, fines and participation in DUI driving training program. The overwhelming majority of tests given are breath alcohol tests, commonly referred to as breathalyzers. The Intoxilyzer 5000 is the predominant breath alcohol testing machine used in Rhode Island. It looks like a grey box similar in size to a VCR, and it has a tube on the side (used for providing the breath sample) and a key board attached to the front.

The Intoxilyzer 5000 works using the scientific principal of infrared absorption. Essentially, this machine works by measuring the amount of light that is absorbed by the present alcohol molecules. A light bulb (positioned at one end of a breathing cylinder) emits a constant infrared light. There are filter wheels at the other end of the same cylinder which captures the light that gets transmitted through. When a person breathes into the cylinder, the infrared light that is being transmitted will make any alcohol molecules absorb the light, preventing it from reaching the other side of the cylinder. The machine calculates the light sent with the light received to determine how many alcohol molecules are present. This calculation is then converted into a value that translates to blood alcohol content. While most prosecutors and police officers wish to breeze by this point, a skilled DUI defense lawyer will have studied the inherent flaw in this value conversion. Remember, the Intoxilyzer 5000 is measuring the level of alcohol in your BREATH. The law, however, makes it illegal to drive with a certain level of alcohol in your BLOOD. What the machine does is translate the breath alcohol concentration into a blood alcohol concentration using a pre-set formula. This translation is commonly referred to as a partition ratio. The average person’s partition ratio, as used by the Intoxilyzer 5000, is 2100 parts of alcohol in the breath for every 1 part of alcohol in the blood. But what if you’re not the average person? What if you have a partition ratio of 1700/1? Unfortunately for you, when the machine makes its conversion, you will have an elevated false reading. What was really a .05 BAC level has just been printed out on the breathalyzer machine at the police station as a .08 and you’re now being booked for a DUI.

Another problem with the accuracy of the Intoxilyzer 5000 is its inability to differentiate between alcohol molecules coming from the subjects lungs (as it assumes) and alcohol molecules coming from the mouth and/or esophagus. Recent vomiting, hiccupping, coughing, crying or having dentures or having acid reflux, liver disease or heartburn, all can cause false, elevated readings on the Intoxilyzer 5000.