If you have been charged with driving while intoxicated (DWI), it is likely that you have undergone a breath analysis test using an intoximeter such as the EC/IR II. Formerly known as breathalyzers, intoximeters are devices that determine blood alcohol content (BAC) by measuring the amount of alcohol in a breath sample.

In North Carolina, law enforcement uses the Intox EC/IR II as its official breathalyzer machine. This device is not a portable breath test (PBT) but is instead administered by a trained chemical analyst at a police station. Unlike PBT results, which are only used to establish probable cause for arrest, blowing a 0.08 or higher on the EC/IR II can be presented as evidence in court to support a DWI conviction. North Carolina law considers the results of a chemical analysis to be sufficient proof of an individual’s alcohol concentration. These results assume that the amount of alcohol detected in a breath sample is equivalent to the amount of alcohol in the body.

To ensure that intoximeter results are admissible in court, specific procedures must be followed and rights must be observed. Issues that can arise with the use of the EC/IR II and other breath-testing mechanisms include:

• You must be informed of your right to have a witness.

• If you do not waive the right, you must be granted 30 minutes to allow the witness to arrive.

• The machine must have been duly and properly calibrated and maintained.

• The chemical analyst must be properly trained and admitted as an expert.

• You must be observed to ensure that you did not consume anything, burp, or vomit prior to blowing, all of which can interfere with the reading.

• At least two breath tests must have been given on the EC/IR II with proper time given between each test.

• The two breath tests cannot be more than 0.02 apart in the results.

The law requires the officer to inform you of your right to decline a breath test, but refusal will result in a one-year license revocation, with the first six months being a period of complete driving ineligibility.

Manufacturers of alcohol breath test machines consistently claim that each new model is significantly more accurate and reliable than its predecessors. This claim is often met with interest by experienced DWI lawyers who have been trying cases in court for years. However, manufacturers rarely acknowledge the flaws in their previous models until a new one is released. As with any machine or computer, alcohol breath test machines are not infallible and can produce erroneous readings. Fortunately, many judges and juries recognize their limitations.

Another important consideration is retrograde extrapolation, which involves estimating your blood alcohol concentration (BAC) at the time of driving based on the results obtained from the EC/IR II, a machine used to measure BAC. However, there is typically a significant time lapse between the time you blow into the machine and the time you were driving, which can affect the accuracy of the results. Retrograde extrapolation attempts to account for this by multiplying the elimination rate of alcohol by the time period in question. The reliability of this process can vary depending on individual factors, but it has been deemed scientifically sound enough to be admissible in court. The State must call an expert witness to present evidence of your BAC at trial using retrograde extrapolation.

Need some guidance?

If you have any further questions about the DWI process (have a look at our FAQs) or need something case specific, feel free to reach out. I am always happy to review a case and give you honest feedback on where you stand and how it should be addressed. I handle DWI defenses out of the following North Carolina areas: All of Pender County (Hampstead, Topsail, Burgaw, Surf City, Atkinson) and New Hanover (Wilmington, Wrightsville Beach, Carolina Beach, Ogden, Monkey Junction).