Ithaca Watkins Glen DWI lawyer: Understanding Difference between RELIABILITY and VALIDITY with NY DWI Breath Testing

Understanding the Difference Between Reliability and Validity 

with New York DWI Breath Testing

Attorney Mike Cyr taking Datamaster DMT Breath Test at DWI seminar Jan. 2016,
Newman & Cyr, The DWI Attorneys

In every New York DWI, case the judge is going to tell the jury by instruction that breath testing or the breathalyzer is reliable. People can be confused that that also means that the BAC number result is also accurate or valid.

Why Reliable and Valid are not the same thing?

Reliable just means something is consistent. It means that it gives the same or similar result every time.

Validity means that something is correct, that it is, in fact, accurate in it’s determination or measurement.

When it comes to New York DWI breath testing even if the machine is consistent in it’s assessment that does not mean it is accurately measuring what it is supposed to measure.

What’s the DWI Chemical Test Supposed to Measure?

Chemical tests of breath samples in DWI arrests are supposed to measure blood alcohol concentration.  What they do is take an alcohol sample run it through a computer to calculate a blood result number.

If a weight scale is set 10 lbs over it will consistently weigh you plus 10 lbs every single time. That does not mean that you way plus 10 lbs. So the scale is reliable (consistent in it’s testing) but not valid.

In chemical breath testing, the machine is set with a blood to breath ratio of 2100:1. This is an average ratio of the population. It is also set at a temperature of 34 degrees. It also assumes that your body is done absorbing alcohol. To arrive at it’s number for you (and many other people) this may be like the scale set to plus 10 lbs. In the chemical breath test situation, this may be like adding .03 BAC to .05 BAC to perhaps a legal BAC under .08 BAC. 

This is an important concept for anybody facing a DWI to understand.

If you have questions about a DWI case in New York, call us:

607-229-5184

or find us online:  www.ithacadwi.com

www.watkinsglendwi.com

www.facebook.com/ithacadwi

www.twitter.com/ithacadwi

BY NEWMAN & CYR
Educational Purposes only. Copyright 2016.

If you or a loved one are charged with a crime, we strongly urge you to consult with a local, licensed criminal defense attorney to lessen the possible negative outcomes -including the potential loss of your freedom.


*Attorney advertising