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Truncation of the Breath Ticket in a Driving While Impaired Case

Many DWIs in North Carolina culminate in a chemical analysis, most of the time conducted on an Intox EC/IR II machine. In some cases, the officer will request a blood draw, and a medical professional will draw a person’s blood and send it off to a crime lab for analysis.

The Intox EC/IR II machine produces a breath ticket. A copy of that ticket is given to the person suspected of having driven while impaired, a copy is placed in the court file, and copies are alternatively sent to the DMV and the DA.

This is a sample breath ticket taken from one of the preventative maintenance checks performed by the folks at the Forensic Tests for Alcohol Branch of North Carolina’s DHS.

The breathalyzer machine is designed to report back results to the thousands decimal point. For example, a Breath Alcohol Concentration might be .085, .079, .105. But, as you can see, the breath tickets in North Carolina report back a result to the hundredth decimal point.

So instead of .085, the machine spits out a result of .08, truncating the result. A .079 is reported back as .07. and a .105 is reported back as a .10.

Prosecutors and police officers like to argue that North Carolina’s rule truncating the number is a benefit to the accused. In State v. Shuping, the North Carolina Supreme Court seemed to accept this argument, denying a defendant’s request to throw out the breath alcohol result because of the large margin of error.

After all, say prosecutors, if the actual result reported by the machine is a .089, but North Carolina’s breath ticket reads .08 then a judge or jury will never know that the result was higher than .080 by .009. (If your head is spinning because of the numbers, keep in mind that I went to law school because I’m also not good at math!)

But is it really true that truncation favors the defendant? No.

And here’s why. The Intox EC/IR II machine is unreliable. While prosecutors claim that it produces a definitive answer about the breath alcohol concentration of an individual, North Carolina code and statutes say that a result is valid so long as the sequential tests from the machine are within .02 of one another.

Therefore, a result of .10 at 12:42 am and .08 at 12:45 am is considered “valid” under North Carolina law, and therefore admissible (assuming all other evidentiary rules are met) in a court of law to show that the defendant had a BrAC of .08 or above at a relevant time after the driving.

However, let’s think about those results in that example. The machine got a reading that it truncated. Maybe the reading was a .109 for the .10 blow and a second reading of a .080 for the lower of the two blows. That means there was a difference of .029 between the two blows. We simply don’t know because North Carolina rules don’t allow us to know because the number has been truncated.

But the difference between two blows taken within 3 minutes of each other can be as much as .029 off or 36 percent different, and yet those results are considered valid!

Let’s assume you are an electrician, and you test the same electrical component twice within two minutes of each other. The voltage is supposed to be constant, but your testing instrument reads voltages that are more than 1/3rd different. Wouldn’t you want to double check your testing instrument.

Prosecutors typical response is that only the lower of the two numbers is typically admissible in court. So even if there is a discrepancy between the two numbers, the lower number in favor of the defendant gets admitted.

The problem with this argument is that there is very rarely a third test. Two numbers are all that are recorded in a typical DWI breath analysis. If they differ, no third test is taken.

For instance, let’s take the example above that a person blew .10 at 12:42 am and a .08 at 12:45 am. Let’s assume that a third blow was taken at 12:47 am and it showed the person blew a .06. That would be a valid blow, and the reported answer. In that case, the person would’ve been, all things being equal, not above the per se limit.

Truncation is a complicated issue, but not necessarily done in favor of the defendant. Truncation hides valuable information from the defendant about just how unreliable these devices are.



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