How Many DUI Breath Tests Are Required?

How Many DUI Breath Test Samples Are Police in Your State Required to Collect?

In some states, you will be asked to give two DUI breath tests to be tested, and the results must be close enough to each other to demonstrate a reasonable degree of consistency. In the other states, any one breath test result is adequate for “legal” purposes, if properly performed.


Mouth alcohol detection is a feature that many manufacturers claim will help prevent false high readings.  However, these drunk detectors are not routinely calibrated for proper performance, and do not work in even half of the cases where some mouth alcohol is present.  Some breath test devices will actually print a false, elevated test result when some alcohol is in your body, and other alcohol from your mouth or esophagus gets added to the sample when you deliver a DUI breath sample.

If two samples are taken, how closely must the results (numbers) be to each other to constitute a valid DUI breath test? 


For the breath test results of either of the samples to be considered accurate enough to be used against you, most states (except a few such as New Jersey and Wisconsin) require multiple tests, and also require that the two results be close enough to each other to demonstrate some measure of scientific “precision” to confirm an appropriate agreement, or the results are thrown out.  This limit of difference on human subject breath testing is typically 0.02 grams, or 0.03 grams in one or two states.  

This difference is allowed because most states require an accuracy of no more than 0.01 in the breath test machine’s variance from a tested simulator sample to a known chemical standard.  Variances in human breathing patterns will not allow reliable dual sample testing with less than a 0.02 grams (plus or minus) variability.


Regulations or statutes are in place that require a testing officer to follow specified DUI protocol


Because scientific DUI breath testing occurs so frequently and a variety of issues are constantly litigated, most police departments have specific protocols with regard to performing this chemical testing.  If you took a State-administered breath test, in light of your presumption of innocence, the prosecution must typically prove that at the time of your test this equipment was in working order, was properly maintained, and that the breath test was administered in a proper fashion, typically according to their protocol.

These protocols are commonly designed out of their experience and in consultation with the prosecutors, as to what is required for an arrest for DUI-DWI to be successfully followed by a DUI conviction.


The best DUI lawyers or DWI attorneys in your area know your state’s protocols for DUI breath testing, and more importantly, the reasons behind the steps in the protocol.  If the protocol for your breath test was not followed, this may imply to the court that there is a problem with either the arrest or with the collection of the DUI police evidence.  While the protocols are put in place to protect the reliability of breath test results collected by the police officers during your arrest, a breach of these protocols may be used in your benefit to have the charges against you be dismissed, reduced or to win at trial.