Breathalyzer and Chemical Tests in Utah

How the Intoxilyzer 9000 Works in Utah DUI Cases

Utah uses the Intoxilyzer 9000, manufactured by CMI Inc., as its evidential breath testing instrument for DUI cases. When the prosecution presents a BAC number at trial, it almost always comes from this device. Understanding how the Intoxilyzer 9000 works, what assumptions it relies on, and where those assumptions break down is central to effective DUI defense in Utah.

The instrument uses infrared spectroscopy to measure the concentration of alcohol molecules in a breath sample. When you blow into the device, the breath passes through a sample chamber where infrared light is directed through it. Alcohol molecules absorb infrared energy at specific wavelengths, and the instrument measures that absorption to calculate the concentration of alcohol in the breath. It then converts the breath alcohol concentration to an estimated blood alcohol concentration using a standard partition ratio of 2,100 to 1, meaning the instrument assumes that 2,100 milliliters of deep lung air contains the same amount of alcohol as one milliliter of blood.

The partition ratio is where the science becomes problematic for individual cases. The 2,100:1 ratio is an average derived from population studies. Actual individual partition ratios range from approximately 1,100:1 to 3,400:1 depending on body temperature, lung capacity, breathing patterns, hematocrit levels, and other physiological variables. A person with a partition ratio lower than 2,100:1 will produce a breath test result that overstates their actual blood alcohol concentration. The Intoxilyzer 9000 has no way to account for this individual variation because it applies the same fixed ratio to every test subject.

This is especially significant in Utah, where the .05 BAC limit is so low that even small measurement errors can mean the difference between a legal and illegal BAC reading. A person whose actual BAC is .04 could produce an Intoxilyzer reading of .05 or .06 simply due to individual physiological variation in the partition ratio. Our page on BAC limits in Utah explains how the low threshold amplifies the impact of testing errors and why precision in chemical testing matters more here than in any other state.

Sources of Error in Breath Testing

Beyond the partition ratio issue, multiple additional sources of error affect breath test reliability. Each one represents a potential defense challenge, and in many cases, more than one applies simultaneously.

Mouth alcohol contamination is one of the most common sources of falsely elevated readings. When alcohol is present in the mouth rather than arriving through deep lung air, the instrument measures a combination of alveolar breath alcohol and oral cavity alcohol, producing a reading that is higher than the actual blood alcohol level. Gastroesophageal reflux disease brings stomach contents, including any alcohol, back into the esophagus and mouth. Recent belching or vomiting has the same effect. Dental appliances, braces, tongue piercings, and periodontal disease can trap alcohol in the mouth. Certain mouthwashes and breath sprays contain alcohol that lingers in the oral cavity. The officer is required to observe the subject for a deprivation period before testing to ensure that no mouth alcohol is present, but the observation must be continuous and attentive. If the officer looks away, checks paperwork, or is otherwise distracted during the observation period, mouth alcohol contamination may go undetected.

Instrument calibration and maintenance affect accuracy directly. The Intoxilyzer 9000 must be calibrated at regular intervals using a solution of known alcohol concentration. If calibration checks are overdue, if the calibration solution has expired, or if the instrument's calibration logs show drift outside acceptable tolerances, the reliability of the test result is compromised. Operator error is another factor. The technician administering the test must follow a specific protocol, including verifying the instrument's operational status, ensuring the observation period was completed, and properly documenting the testing process. Deviations from protocol create grounds for suppression or credibility challenges.

Radio frequency interference from nearby electronic devices can affect the Intoxilyzer's readings. Temperature variations, both in the testing environment and in the subject's body, influence the breath test result because alcohol vapor pressure changes with temperature. An elevated body temperature from illness, physical exertion, or even prolonged sitting in a heated patrol car can produce higher breath test readings than the subject's actual BAC would warrant.

Glen Neeley owns an Intoxilyzer 5000EN, which allows him to study the mechanics of infrared breath testing firsthand and demonstrate testing principles during hearings and trial. He has completed the Borkenstein Course on alcohol and highway safety at Indiana University, the leading educational program on alcohol testing science. That combination of hands-on instrument experience and formal scientific education gives Glen a level of technical fluency that directly strengthens his ability to challenge breath test evidence in every case.

Blood Testing, Chain of Custody, and Lab Analysis

When a blood test is used instead of or in addition to a breath test, the analysis measures actual blood alcohol concentration rather than estimating it from breath. Blood tests are generally considered more accurate than breath tests, but they are far from infallible. The reliability of a blood test result depends entirely on whether strict procedures were followed at every stage, from collection through analysis.

The blood draw must be performed by a qualified phlebotomist using an approved collection kit. The collection site on the skin must be cleaned with a non-alcohol-based antiseptic; using an alcohol swab can introduce external alcohol into the sample. The collection tube must contain the correct preservative, typically sodium fluoride, to prevent the blood from fermenting and producing alcohol after collection. It must also contain an anticoagulant, typically potassium oxalate, to prevent clotting. The tube must be properly mixed and stored under refrigeration. Delays in refrigeration or analysis can lead to degradation of the sample or microbial growth that generates alcohol within the tube itself.

Chain of custody documentation tracks the sample from the moment it is drawn through delivery to the lab, storage at the lab, analysis, and reporting of results. Any gap in the chain of custody raises questions about whether the sample was properly handled, whether it could have been switched or contaminated, and whether the result can be reliably attributed to the defendant. Glen Neeley examines lab reports, collection records, refrigeration logs, and chain of custody documentation in every blood test case. He also reviews the lab's quality control records, analyst qualifications, and instrument maintenance history to identify potential weaknesses in the analysis itself.

The timing of the blood draw matters as well. Alcohol absorption continues after your last drink, and your BAC may still be rising at the time blood is drawn at the station. If the draw occurs during the rising absorption phase, the measured BAC may be higher than your BAC was at the time you were actually driving. This rising blood alcohol defense requires retrograde extrapolation calculations that involve assumptions about absorption rates, elimination rates, food consumption, and individual metabolism. Glen's completion of the Borkenstein Course gives him the scientific foundation to evaluate and challenge these calculations effectively.

Fermentation is another concern in blood testing. If the blood sample does not contain sufficient preservative, or if the preservative has degraded, microorganisms in the blood can produce alcohol through fermentation after the sample is collected. This means a blood sample can show a higher BAC than was actually present at the time of the draw. Proper preservative levels, prompt refrigeration, and timely analysis guard against this problem, but failures in any of these steps occur more frequently than labs typically acknowledge. Independent retesting of the sample, when sufficient volume remains, can reveal discrepancies between the original result and a subsequent analysis that undermine the prosecution's BAC evidence.

As a board-certified DUI defense attorney through the National College for DUI Defense and an NCDD faculty member who has been practicing since 1998, Glen brings both the scientific knowledge and the courtroom experience to challenge chemical test evidence effectively. Whether your case involves a breath test, a blood test, or both, the reliability of that evidence is never assumed; it is verified and challenged at every step. The .05 BAC limit in Utah, discussed in detail on our BAC limits page, makes the precision of chemical testing more consequential here than in any other state because even small errors can move a reading across the legal threshold. For information about how chemical testing fits into the arrest sequence, see our page on the DUI arrest process. For information about the penalties a chemical test result can trigger, see our page on DUI penalties in Utah.