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The DWI Defense Lawyers of Kurtz & Blum in Raleigh, North Carolina, Discuss the Technology Commonly Used in DWI Cases

DWI Lawyers Talk Intoximeters, Retrograde Extrapolation, and Other Technology Used in Impaired Driving Investigations

If you have been arrested and charged with a DWI, you have most likely encountered an intoximeter, or breath analysis test, such as the EC/IR II.  Intoximeters, sometimes know by their older names of breathalyzers, are devices that measure blood alcohol content (BAC) from a breath sample.

The Intox EC/IR II is the breathalyzer machine used by North Carolina law enforcement.  It is not a portable breath test (PBT), but a device used at police stations by a trained chemical analyst.  Unlike the result from a PBT, which is just used for obtaining probable cause for arrest, blowing at or over the legal limit of 0.08 on the EC/IR II can be used as evidence at trial to convict you of a DWI.  In fact, North Carolina law states that the results of a chemical analysis are sufficient proof of your alcohol concentration.  The results from an intoximeter assume the amount of alcohol on your breath is the same as that in your body.

There are a number of specific procedures that must be followed and rights that must be recognized for the results of an intoximeter to be allowed into court.  A list of issues that arise with 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 or burp or vomit prior to blowing into the machine, 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.

An officer must also inform you that you have a right to refuse taking a breath test, but your license will be revoked for a year if you do so.  Again, you can refuse to take a breath test, but, as a result, you will lose your license for one full year, the first six months of which you will be ineligible for a privilege.

With each new model of alcohol breath test machines developed, the manufacturers claim that it is now amazingly accurate.  For those of us who have been trying DWI cases in court for years, it is always interesting to hear how much better they claim the new tests are and how much more reliable and accurate they are.  What they are repeatedly saying is that the last models were flawed.  They don’t tell anyone that until the new model comes out.  Like any other machine or computer, intoximeters give incorrect readings and make mistakes.  Luckily there are judges and juries who do recognize their limitations.

Another issue to consider is that of retrograde extrapolation.  Much time has generally passed by the point you first blow into the EC/IR II, which means the result does not measure your BAC at the time you were driving.  Retrograde extrapolation is the process used to judge your BAC at the time you were driving based on the results from the EC/IR II by multiplying the elimination rate of alcohol by the time period in question.  The results of eliminating alcohol from the body can vary greatly depending on the person and other conditions, but retrograde extrapolation has nonetheless been considered to be sufficiently scientifically reliable to be admitted at trial.  To admit evidence of your BAC at court from retrograde extrapolation, the State must call an expert witness.

The DWI attorneys at Kurtz and Blum are all too familiar with the EC/IR II and other breath testing technologies.  They have the experience and savvy you need to challenge the procedures used during your intoximeter test as well as the results. 

We regularly help people in Wake County, North Carolina.  We frequently handle offenses arising out of the following cities: Fuquay-Varina, Rolesville, Wendell, Knightdale, Raleigh, Morrisville, Wake Forest, Zebulon, Holly Springs, Garner, Cary, Apex and New Hope.