Ross Koplin

Colorado Driver Blood Alcohol Content (BAC) Testing and Measurement For DUI and DWAI

What is Blood Alcohol Content or BAC?

What is Blood Alcohol Content or BAC?

What is Blood Alcohol Content or BAC?

In the state of Colorado, the level of intoxication of a motorist from alcohol is measured by a BAC or Blood Alcohol Content scale. The BAC scale is the standard for measuring the amount of alcohol in a person’s blood at any given time. This scale is represented by a number that is generally as low as 0.00 and can be as high as 0.45. There are several different tests that can measure Blood Alcohol Content (BAC).

The Roadside Sobriety Tests

The initial tests typically administered to a Colorado motorist stopped for being suspected of Driving Under The Influence (DUI) are Roadside Sobriety Tests. These are typically a series of tests meant to ascertain whether a person has had alcohol in sufficient quantities to make their level of coordination, and their general ability to drive, inferior to a person who has not had any alcohol. These are screening tests and, although they can ostensibly determine a general level of intoxication, these tests do not provide an actual measurement of Blood Alcohol Content (BAC).

The Preliminary Breath Test or PBT

The first potential test for measuring BAC that is commonly given at the time of an alcohol stop is called a PBT or Preliminary Breath Test. The device used to administer a PBT is a small, handheld testing unit that are commonly in police patrol cars. The test administered through the use of a PBT is often unreliable and the results of a PBT test are not admissible as evidence in court.

Do I have to take the Roadside Sobriety or Preliminary Breath Tests?

Roadside Sobriety Tests and Preliminary Breath Tests are both utilized as screening tests. Prior to making an arrest, if the officer does not have a warrant, which is typically the circumstance in a DUI stop, the officer must generally have probable cause to believe that a crime has been committed and that the individual suspected is the perpetrator of that crime. Both the Roadside Sobriety Tests, and the Preliminary Breath Test are utilized to develop probable cause for the officer to thereby justify an arrest of a motorist. An individual has the right to refuse the Roadside Sobriety Tests, and to refuse the PBT and, if the individual refuses either or both, this is not considered a refusal under Colorado’s Express Consent Law leading to a loss of driving privileges.

The DUI tests that matter and Refusals under Colorado’s Express Consent Law

The important tests for Blood Alcohol Content (BAC) are given at the police station, a hospital or some facility that can be used to administer such a test. A motorist involved in a routine traffic stop is generally entitled to choose between a breath test or a blood test. The breath test typically administered at a police facility is done through the use of an Intoxilyzer 5000 machine. This is a desk top machine that is considered more accurate than a Preliminary Breath Test (PBT).

Results from a blood test, and the breath test using an Intoxilyzer, are normally admissible as evidence. A motorist in Colorado has the right to refuse these tests, however, a refusal is a violation of the Colorado Express Consent Law. Thus, a refusal has adverse implications for the driving privileges of the individual who refuses such a test. If an individual refuses such testing the fact that the test was refused can itself be used as evidence against an individual in a Colorado Court. However, if such a test is refused the prosecution is generally left without any specific reliable test as to the level of intoxication of a motorist and thus a prosecution is normally subject to countervailing arguments as to whether the person was, or was not, intoxicated, at the time of the arrest.

How are these Blood Alcohol Content tests scored?

An individual twenty-one (21) or older whose Blood Alcohol Content (BAC) score on a blood test, or a breath test using the Intoxilyzer, is less than 0.05, is considered presumptively not to be under the influence and not impaired by alcohol. If the Blood Alcohol Content (BAC) is greater than 0.05, but less than 0.08, then in Colorado this gives rise to the permissible inference that the motorist was Driving While Ability Impaired (DWAI). This offense is less serious than Driving Under The Influence and the person is thereby subject to slightly lesser penalties.

If BAC, as measured by a blood test, or a breath test administered through an Intoxilyzer, is 0.08 or higher, then the person will, among other offenses, likely be charged with a DUI Per Se. DUI Per Se is a crime in Colorado based on the Blood Alcohol Content (BAC) of a motorist being above the limit of 0.08 as determined by a lawful test.

Conviction of DUI without a BAC Test

In the state of Colorado, a person can also be convicted of a DUI under a subjective standard which provides that an individual was Driving Under the Influence if the individual was substantially incapable of driving a motor vehicle. This is often typically largely based upon a police officer’s testimony. Thus if the police officer can convince the jury that a motorist was intoxicated by testifying as to specific behaviors or actions (i.e. swerving, having an accident, disorderly behavior, roadside sobriety tests etc.), the person can be found guilty of a DUI regardless of whether the person was tested for BAC or not.

This is another reason why having an experienced Colorado DUI attorney represent you is so important. Your Colorado DUI lawyer will review both the alcohol test you were given and the officer’s observations at the time of your arrest and challenge any unfair evidence presented.

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Legal Disclaimer – The information contained at this web site is not intended to be legal advice and all information regarding Colorado criminal law is general content only and should not be relied upon for any specific Colorado criminal law situation. Information on this web site is not intended to be comprehensive and does not cover all the issues, nuances or ramifications related to the topic discussed. This web site may not be updated routinely to reflect the very most current Colorado law.

Individuals should consult an experienced Denver criminal attorney, Denver DUI laywer, or Denver traffic lawyer for advice regarding an individual situation. 

by Ross Koplin


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Ross E. Koplin, Attorney at Law

(303) 831-8924
600 17th Street, Suite 2800 South Denver, Colorado 80202

Ross Koplin is a Traffic Attorney serving the Denver Metro area who provides quality legal representation to those involved in traffic misdemeanors, including prosecution for traffic tickets, speeding tickets, driving under the influence of alcohol or drugs (DUI), or other traffic offenses.

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