Colorado DUI Chemical Tests: Breath, Blood or Refuse?

Colorado drunk driving tests - choose or refuse?

By driving in Colorado, you give your express consent to a chemical test for alcohol and/or drugs if you are lawfully arrested for:

Most of the time, you will be asked to choose whether to take a breath test or a blood test. This chemical test is used to determine your “BAC." Your BAC is your blood alcohol concentration (sometimes referred to as your blood alcohol content).

To help you decide which DUI test to take, our top Colorado DUI defense lawyers discuss the following:

Also see our general article on Colorado DUI chemical tests: Breath, blood, refuse?

1. What is the difference between a preliminary breath test and an evidentiary breath or blood test?

When a Colorado law enforcement officer pulls you over, you may be asked to take a preliminary breath test (PBT) on a handheld breath analyzer. The preliminary breath test is not mandatory. It is a roadside sobriety test that can help the officer decide whether to arrest you or let you go. You may refuse a preliminary breath test without consequences.

If, however, you are placed under arrest, an evidentiary chemical test is required. Usually, it will be given at the station or another official location after you are placed under arrest.

2. Can I refuse to take a breath or blood test?

Refusal to take a DUI chemical test results in serious consequences. Penalties for refusing a DUI chemical test include:

    • Automatic suspension of your Colorado driver's license for one year, 
    • Designation as a Colorado “persistent drunk driver" (PDD),
    • Mandatory level II alcohol and drug education and treatment program before your driving privilege can be reinstated,
    • Ignition interlock restricted license for at least one year following reinstatement,
    • SR-22 insurance even if you are not guilty of DUI, and
    • Admissibility of your refusal to take a chemical test as evidence of guilt.

3. Can I choose which Colorado DUI test to take?

In most circumstances, the officer must offer you the choice of a DUI breath test or a DUI blood test. The exceptions are when:

  • there is probable cause to believe drugs caused or contributed to your violation (blood, urine and/or saliva required),
  • you are under 21 and the only violation is UDD (breath test only),
  • you have a medical condition that prohibits a particular test,
  • you are unconscious (or dead), or
  • extraordinary circumstances (such as weather or equipment malfunction) prevent completion of your preferred test within two hours.

4. Should I choose a DUI breath test or DUI blood test?

Unfortunately, there is no easy answer as to the best test to pick if you are arrested for drunk driving in Colorado. Each test has its advantages (see below), as does refusing to take a chemical test at all. Keep in mind, too, that if you are, in fact, intoxicated, you might not be thinking as clearly as you are now.

The important thing is to be as polite as possible to the officer. Your chemical test is not the only evidence that will be used against you. And whatever you choose to do, remember that a skilled Colorado DUI defense lawyer can challenge it.

4.1 Advantages of a Colorado DUI breath test

Most people arrested for DUI choose to take a breath test. The main advantages of a breath test are:

  • a breath test is less invasive than a blood test, and
  • everyone has a different partition ratio (explained below).

DUI breath tests do not measure the amount of alcohol in your blood directly. Rather they mathematically convert the trace amounts of alcohol in your breath to an equivalent BAC. This is known as a “partition ratio.”

Colorado uses a partition ratio of 2,100 to 1. It assumes that 2,100 milliliters of alcohol in your breath is equivalent to the alcohol in 1 milliliter of your blood.

However, not everyone's lungs absorb alcohol from their blood at the same rate. Colorado's 2,100:1 partition ratio is simply an average. Actual ratios vary widely. Even your personal partition ratio can change from day to day. In particular, it changes depending on your body temperature and the temperature in the room.

Colorado – unlike some other states – allows evidence of differing partition ratios to be presented to the jury. So if you are close to the legal limit, it may be easier to create reasonable doubt with a breath test. This is especially true if there is little or no independent evidence that you were actually too inebriated to drive safely.

4.2 Advantages of a Colorado DUI blood test

The main advantages to a DUI blood test are:

  • A DUI blood test is more accurate than a breath test,
  • The results must be confirmed by two different methods, and
  • You have the right to submit your blood for independent testing.2

4.3 Advantages of a chemical test refusal

The only possible advantage to refusing a chemical test is that there will be no way to prove you were over the legal limit. The prosecution will have to prove your guilt by showing you were actually under the influence or ability impaired.

If the prosecutor is unable to do this, you will not be sent to jail. However, in most other ways you will be treated as if you are guilty, but with a longer license suspension. Your refusal to take a chemical test is also admissible as evidence of guilt. And it is harder–though not impossible--to defend a chemical test refusal.

Call us for help…

call center receptionist

Were you charged with a DUI, DWAI, UDD or chemical test refusal in Colorado? Our compassionate Denver DUI lawyers have a great deal of experience challenging DUI test results. Contact us today and find out how we can fight to keep you out of jail and protect your driving privilege.

Our Denver office can be found at:

Colorado Legal Defense Group
4047 Tejon Street
Denver, CO 80211
(303) 222-0330

Legal references:

  1. 42-4-1301.1 C.R.S.
  2. 5 CCR 6.2.3.


Free attorney consultations...

The attorneys at Shouse Law Group bring more than 100 years collective experience fighting for individuals. We're ready to fight for you. Call us 24 hours a day, 365 days a year at 855-LAW-FIRM for a free case evaluation.

Regain peace of mind...

Shouse Law Defense Group has multiple locations throughout California. Click Office Locations to find out which office is right for you.

Office Locations

Shouse Law Group has multiple locations all across California, Nevada, and Colorado. Click Office Locations to find out which office is right for you.

Call us 24/7 (855) 396-0370