In Colorado, if an officer has probable cause to believe you’ve committed DUI, they’ll probably request you take a blood or breath test. DUIs can be filed as either a Colorado misdemeanor or a Colorado felony, depending on the officer and the circumstances. Being under suspicion for DUI for the first time in Colorado can be intimidating.

The criminal defense team at McDermott Stuart & Ward has represented clients for years in resolving issues related to drinking and driving, marijuana-impaired driving, and other such charges. We have created a list of items to remember if you are pulled over for a Colorado DUI on the 4th of July or any other holiday.


  1. Do you have to say yes to a DUI blood test or breathalyzer test in Colorado?

No. While it is true that by driving on the roads of Colorado, you have expressly consented to a test of your blood or breath, you are still allowed to refuse a breath or blood test.[1]


  1. What happens if I refuse to take a blood or breath test and I am suspected of a DUI in Colorado?

It is your right to refuse a blood or breath test but if you do and you are convicted, your punishment is automatic. Your driver’s license will be revoked for one year.[2] Additionally, the prosecutor is allowed to admit evidence of your refusal to take a sobriety test at trial.[3] It’s also possible that, even if you refuse, an officer may simply get a warrant authorizing the collection of your blood.[4] Learn more about the two paths regarding Colorado DUIs from the Colorado Department of Motor Vehicle website.


  1. Is the officer allowed to only offer one type of DUI sobriety test in Colorado?

The Expressed Consent statute allows you to choose between blood or breath.[5] There are, however, a few exceptions to this rule:

  • If an officer has probable cause to believe you are driving under the influence of drugs, they may only offer you a blood test.[6]
  • If you choose a breath test but cannot physically blow into the breathalyzer machine (because of asthma, COPD, etc.), you may only be offered a blood test.[7]
  • If you are being treated at a hospital or other location with no access to a breathalyzer machine, you may only be offered a blood test, but this exception only applies if there are “extraordinary circumstances” beyond the officer’s control. According to the Expressed Consent statute itself, an officer may not claim “extraordinary circumstances” just because they’re too busy, understaffed, or find it inconvenient to get you to a breathalyzer machine.[8]

Learn more about Colorado’s Expressed Consent statute.


  1. What is the tiny breath device officers sometimes ask people to blow into on the side of the road to test for alcohol? An alcohol blow test is generally referred to as a breathalyzer.

The small version used for roadside testing is called a Preliminary Breath Test (“PBT”). Officers don’t always ask people to blow into it, but if they do, it’s usually to see if the result is high enough to contribute to a finding of probable cause for DUI.

PBT results are problematically unreliable, though. So unreliable, in fact, that Preliminary Breath Test or PBT are inadmissible in all Colorado courts.[9]


  1. Should I pick a blood or breath test if I am suspected of a DUI?

The pros and cons of each blood and breath test are dependent on the circumstances of your Colorado criminal case. An experienced lawyer will know the technicalities affecting each type of test.  Some examples include:


Blood   Breath
  • How the collection site is prepared;
  • Using expired or unsuitable tubes (called “vacutainers”);
  • Misarranging the samples on the lab tray before analysis;
  • Poor or lacking quality assurance procedures within the toxicology lab;
  • The length of time before your blood result is finally provided; or,
  • The cost and opportunity to retest a sample.


  • The presence of mouth alcohol;
  • Foreign objects in the mouth, including braces, a retainer, or dentures;
  • Health conditions like diabetes or COPD;
  • Being in a state of ketosis at the time of the test;
  • Frequently working with acetone or isopropyl alcohol;
  • Burping or vomiting before the test;
  • Nearby radio frequencies affecting the intoxilyzer machine;
  • Increased body temperature (from a hot day, sunburn, or time spent in a hot tub);
  • Improperly calibrated intoxilyzer machines;
  • Exhaling an overabundance of breath volume into the intoxilyzer machine;
  • Uncertified intoxilyzer facilities; or,
  • Issues with the software or hardware of the intoxilyzer.


Only an attorney skilled in litigating DUIs will understand all the intricacies of blood and breath tests. The best way to make sure all evidence in your case is fully investigated is to work with someone who knows all the ins and outs of the charge and is willing to put in the work to defend against it.

Top Colorado DUI Attorneys

In Colorado, your chances are better when you hire a lawyer for a DUI or a DWAI.

The criminal defense team at McDermott Stuart & Ward has great experience in defending and dismissing DUI charges.

Call today for a free consultation with one of our lawyers at (303) 832-8888.


Citation Sources:

[1] § 42-4-1301.1, C.R.S. ­

[2] § 42-2-126(3)(c), C.R.S.

[3] § 42-4-1301(6)(d), C.R.S.

[4] People v. Raider, 516 P.3d 911 (Colo. 2022).

[5] § 42-4-1301.1(2)(a)(I), C.R.S. (“Except as otherwise provided in this section, if a person who is twenty-one years of age or older requests that the test be a blood test, then the test shall be of his or her blood; but, if the person requests that a specimen of his or her blood not be drawn, then a specimen of the person’s breath shall be obtained and tested.”).

[6] § 42-4-1301.1(2)(b), C.R.S.

[7] § 42-4-1301.1(2)(a)(II), C.R.S.

[8] § 42-4-1301.1(2)(a.5)(IV), C.R.S.

[9] National Highway Traffic Safety Administration & International Association of Chiefs of Police, DWI Detection and Standardized Field Sobriety Testing Participant Manual (2023). Link

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