Several of the defenses that we use to help clients beat DUI charges in Colorado are to show that:

1. The police lacked reasonable suspicion to pull you over.
2. The police gave inaccurate field sobriety test instructions.
3. The police lacked probable cause to arrest you.
4. Your blood/breath test results were inaccurate.
5. There were no witnesses, or the witnesses gave inconsistent testimony.

If you or someone you know has been charged with DUI, DWAI or a violation of Colorado’s underage drinking and driving (UDD) law, we invite you to contact us for a consultation.

There are many defenses to driving under the influence or while ability impaired. The best defense is the one that works for you.

Below are 20 of the most common Colorado DUI defenses. We invite you to click on the appropriate link or browse the entire article to learn more.

• 1. Faulty Breath Tests
• 2. Inaccurate Breath Results
• 3. Residual Mouth Alcohol
• 4. Diet/Medical Condition
• 5. Unique Partition Ratio
• 6. Faulty Blood Tests
• 7. Inconsistent Blood Results
• 8. Inaccurate Blood Results
• 9. Rising Blood Alcohol
• 10. Illegal Traffic Stop
• 11. No Miranda Rights
• 12. No Choice of Tests
• 13. Illegal Blood Test
• 14. Non-DUI Symptoms
• 15. Non-DUI Impairment
• 16. Faulty FSTs
• 17. Illegal Checkpoint
• 18. Inconsistent Testimony
• 19. No Impairment
• 20. You Were Not Driving

1. Faulty Breath Tests

Colorado has strict procedures to ensure the accuracy of DUI chemical tests.¹ Yet DUI tests for blood alcohol concentration (BAC) are performed by human beings, and humans sometimes make mistakes. Even a small procedural error can produce a false positive in your BAC result.

Procedural errors with your DUI breath test might include:

• The breath testing instrument was not properly calibrated,
• The breath testing operator was not properly trained,
• The operator failed to observe you for 20 minutes before beginning testing,
• You were not tested within two hours of your driving,²
• Your breath sample was improperly handled, or
• Accurate records were not kept.

Keep in mind that under CRS 42-4-1301(1)(f), strict compliance with Colorado chemical testing regulations is not required for the results of the test to be admissible at trial. Only when the noncompliance is severe enough to impair the validity and reliability of the testing method will the results be excluded entirely.

Otherwise, the failure to follow procedures is just one fact for the jury to consider. However, sometimes that alone is enough, especially in borderline cases.

2. Inaccurate Breath Results

A DUI breath test can produce a false positive even when conducted properly. Reasons your DUI breath test could show a falsely high BAC include:

• Your body temperature,
• The temperature of the room,
• Interference from background radiation, and
• Individual factors such as your personal partition ratio and medical condition (both discussed below).

3. Residual Mouth Alcohol

When you drink, some of the alcohol lingers for 15 to 20 minutes in the mucosal linings of your mouth. This is known as “residual mouth alcohol.”

Residual mouth alcohol can taint the results of evidentiary breath alcohol testing (EBAT). This is because it takes, on average, 50 minutes to two hours before the alcohol you drink passes through

• your stomach and
• into your bloodstream.

Thus it is possible for the residual alcohol in your mouth to “trick” the EBAT machine, even though you might not have consumed enough alcohol to make you drunk. (It can also occur when not enough time has passed yet for the alcohol to make it to your bloodstream—a problem known as rising blood alcohol and discussed below).

To avoid measuring residual mouth alcohol instead of deep lung air, the EBAT operator must observe you continuously for 20 minutes before beginning the test. If this time period is not strictly observed, your breath test could be contaminated by mouth alcohol from:

• recently consumed alcohol (“one for the road”),
• anything you drink during the observation period,
• cough syrup or other medicines containing alcohol,
• other products – such as mouthwashes or breath sprays — that contain alcohol,
• alcohol-soaked food trapped in braces or other dental work,
• burped or regurgitated alcohol,
• reflux caused by medical problems such as GERD, acid reflux or heartburn (discussed below).

4. Diet/Medical Condition

Certain medical conditions can contaminate your DUI breath test results. These include the following:

GERD, Acid Reflux, or Heartburn

In these conditions, stomach contents can back up into your esophagus. When you take a breath test, this can cause extra alcohol to register.

If you suffer from gastroesophageal reflux disease (GERD), acid reflux, or heartburn–or even if you have just eaten a very heavy meal–the result could be a falsely high BAC reading on your EBAT.

High-Protein Diets

Under normal conditions, we get energy from eating carbohydrates, which our digestive system breaks down into sugars. One such sugar is glucose (also known as “blood sugar”), which is our bodies’ primary fuel.

When your body does not get enough carbohydrates, it turns to stored fat for energy. This is the principle behind low-carbohydrate / high-protein diets such as

• Atkins,
• Paleo and
• Dukan.

However, “burning” fat for energy produces a waste product known as ketones. When eliminated from your body through breath and urine, ketones convert into isopropyl alcohol. DUI breath testing machines can sometimes mistake isopropyl alcohol for ethyl alcohol, the kind found in alcoholic beverages.³

Diabetes (Hyperglycemia) or Hypoglycemia

Once the carbohydrates you eat are broken down into sugars, glucose normally enters your bloodstream from your small intestine. Your pancreas then releases the hormone insulin to help deliver the glucose to your muscles and organs.

However, if you have diabetes (hyperglycemia), your pancreas either:

• produces little or no insulin (type 1 diabetes) or
• resists insulin’s effects and/or produces insufficient insulin (type 2 diabetes).⁴

Without insulin, your body cannot metabolize glucose for fuel. It has to use fat, which is broken down in your liver.⁵

When your liver breaks down fat, it produces toxic waste acids known as “ketones.”⁶ Ketones are similar to isopropyl alcohol (acetone). EBAT testing devices sometimes mistake them for ethyl alcohol, the type of alcohol found in alcoholic beverages.

Too many ketones in your system can also cause diabetic ketoacidosis (“DKA”). DKA is a potentially life-threatening condition with symptoms that resemble alcohol impairment.⁷ These can include:

• excessive thirst or dry mouth,
• frequent urination,
• sluggishness,
• a flushed face,
• nausea and/or vomiting,
• confusion,
• decreased coordination, and
• breath that smells fruity and can be mistaken for alcohol.

5. Unique Partition Ratio

Colorado breathalyzers use an average rate — or “partition ratio” – that assumes that the amount of alcohol in 2,100 milliliters of your breath is the same as the amount of alcohol in 1 milliliter of your blood. However, your actual partition ratio may differ. For instance,

• your body temperature and
• the temperature of the room in which the test is given

can affect the amount of alcohol in your breath.

Therefore, we can present evidence of partition ratio variations to the jury, particularly when your BAC is at or close to one of the following thresholds:

• .02% BAC for a UDD,
• .05% BAC for a DWAI,
• .08% BAC for a DUI per se,
• .15% BAC for a “persistent drunk driver” designation.

6. Faulty Blood Tests

Colorado regulations provide strict procedures for DUI blood tests.⁸ Failing to observe them can compromise EBAT results and lead to falsely high BAC readings.

DUI blood testing errors include (but are not limited to):

• blood drawn by an improperly trained technician,
• improperly mixed preservatives,
• test performed by an unaccredited lab,
• improper labeling of your blood sample,
• improper storage of your blood sample, or
• failure to maintain proper records.

7. Inconsistent Blood Results

Even with no human error, DUI blood tests can give imperfect results. This is why Colorado regulations provide that the lab must

• save a portion of your DUI blood sample for one year and
• make it available to you for independent testing.

If a properly certified independent laboratory comes up with results lower than the lab the police used, the court will give you the benefit of the doubt. This is the most significant advantage of choosing a DUI blood test over a DUI breath test.

8. Inaccurate Blood Results

Sometimes, even when everything is done right, blood samples go bad. Ways a DUI blood sample can turn bad include:

• fermentation of your blood or
• contamination of your blood.

This can happen if

• the preservatives are not mixed properly, or
• your blood is not stored at the proper temperature.

Plus there is always the possibility of lost or misplaced records of conditions or chain-of-custody.

9. Rising Blood Alcohol

It takes your body from 50 minutes to two hours, on average, to fully absorb alcohol into your system. So if you are pulled over shortly after drinking, you might be perfectly capable of driving.

However, your BAC would still be rising. By the time of your evidentiary DUI breath or blood test, your BAC might be over the legal limit.

In Colorado, rising blood alcohol is not as strong a defense when the charge against you is

• DUI per se or
• UDD.

This is because these crimes are based solely on BAC as measured at the time you drove or within two hours after.

However, if the charge against you is based on actual impairment (rather than being over Colorado’s “legal limit” for DUI or UDD), rising blood alcohol can be a powerful defense. We may be able to show that because your blood alcohol was on the rise, you were not yet impaired at the time you were pulled over.

10. Illegal Traffic Stop

A law enforcement officer must have reasonable suspicion before you can be:

• pulled over for a traffic violation or
• detained for a DUI investigation.

Plus, police must have probable cause before you can be:

• arrested for DUI, DWAI or UDD or
• required to take an evidentiary chemical test.

If there was no reasonable suspicion to pull you over, any evidence obtained from the illegal traffic stop should be suppressed. As a result, evidence of your lack of sobriety—and often the entire case—will be thrown out of court.

At the very least, the loss of evidence can be used to negotiate a plea bargain to a less serious charge (such as a traffic violation).

11. No Miranda Rights

Despite what you might have seen on TV, the police do not need to read you your Miranda rights until:

• you have actually been arrested, and
• the officer is conducting a custodial interrogation, which is where an officer asks you questions designed to solicit incriminating responses.

If these conditions have been satisfied, the officer must advise you of your Miranda rights. Any statements you make when such a warning has not been given should be excluded from evidence. Depending on how significant those statements are, the case against you might be

• reduced or
• even dismissed altogether.

Keep in mind that you are not protected from answers you gave to questions the officer asked prior to your arrest. So if you are pulled over for an alleged traffic violation, beware of answering questions that could tend to incriminate you on a drunk driving offense.

12. No Choice of Tests

If you are arrested in Colorado on suspicion of DUI, DUI per se, or DWAI, you must ordinarily be offered a choice between a

• breath test and
• blood test.

The exception is if the officer reasonably suspects your intoxication was caused in whole or in part by drugs. In that case, the officer can require that you take a blood, urine, or saliva test.⁹

If you were required to take a blood test but there was no reasonable basis for suspecting drugs, the blood test results can be thrown out.

13. Illegal Blood Test

If after your DUI arrest the police forced you to submit to a blood draw without getting a warrant first, the results cannot be used against you in most DUI cases.

The only times the police do not have to get a warrant before forcing you to take a blood test is if they have probable cause to believe that you have committed either:

14. Non-DUI Symptoms

Indirect evidence of intoxication often comes from the arresting officer testifying that you had:

• red and/or watery eyes,
• a flushed face,
• slurred speech,
• an unsteady gait, and
• the odor of alcohol or marijuana on your breath or in your car.

Even if accurate, however, these signs or symptoms do not necessarily mean you were intoxicated. Innocent reasons for these signs might include:

• you were tired,
• you had allergies,
• you were dehydrated,
• you had been in the sun,
• you were nervous,
• you were ill,
• you were injured,
• you had a headache (or other ache), or
• you have a speech impediment

15. Non-DUI Impairment

While the police like to think that all bad drivers must be DUI, we know this is not the case. While not necessarily legal, the following are all reasons not related to drugs and/or alcohol that could have caused your bad driving:

• you were on the phone,
• you were looking at your computer,
• you were listening to the radio,
• you were in a hurry,
• you were angry,
• you were picking up something that had fallen under the seat,
• you had an animal in the car,
• you were talking with a passenger,
• you were reading a billboard,
• there was a bug in the car, or
• you just had a fight with someone.

In short, drugs and alcohol are not the only explanation for bad driving. Sober people drive badly, too.

If you do any of the above, you may receive a ticket. Though you should not be labeled a drunk driver.

16. Faulty FSTs

Police in many parts of Colorado use Standardized Field Sobriety Tests (SFST) approved by the National Highway Traffic Safety Administration (NHTSA) to determine whether to arrest you for drunk driving. These tests are generally admissible as evidence to prove you were not sober when you drove.

However, there are often innocent explanations for poor performance on field sobriety tests. These can include:

• nervousness,
• being elderly,
• being overweight,
• bad feet,
• poor standing balance generally,
• officer-induced intimidation,
• bad weather conditions,
• poor lighting,
• uneven surface conditions,
• awkward footwear, such as boots, dress shoes or high heels, and/or
• unclear instructions.

Even when performed under ideal conditions, Colorado field sobriety tests are not completely accurate indicators of alcohol and/or drug impairment.¹⁰ In particular, as BAC levels fall, FSTs become less accurate.

By carefully examining the conditions under which an FST was conducted, a skilled Colorado DUI defense attorney may be able to cast doubt on the results.

17. Illegal Checkpoint

Normally police in Colorado must have probable cause to stop and question you if you are driving. This means observing either:

• a traffic violation,
• a defect in your vehicle that affects safety, or
• a driving pattern that indicates you may be intoxicated.

DUI roadblocks are an exception to this rule. However, they must comply with requirements set forth by

• the U.S. Supreme Court and
• the Colorado Department of Transportation.¹¹

Potential problems with DUI sobriety roadblocks include:

• The department had no official procedures for roadblocks in place.
• The site chosen for the roadblock created a traffic hazard.
• The method for selecting which cars to stop was not neutral.
• There was an inadequate warning of the upcoming checkpoint.
• There were inadequate signs of the officers’ authority (such as uniformed officers and marked police vehicles).
• There were no convenient reasonable procedures for DUI breath testing.
• There was no drug recognition expert (DRE) to determine whether drugs other than alcohol were involved.
• There was inadequate briefing by the supervising officers.
• There was inadequate publicity to notify you and other drivers of upcoming DUI sobriety checks.

18. Inconsistent Testimony

The law enforcement officer who arrested you is not the only one who can testify as to whether you were driving safely. Our DUI attorneys work with private investigators who know how to interview witnesses.

When we can find witnesses willing to testify that you were driving safely, we can establish reasonable doubt that you were too drunk to drive. Even when the charge is based solely on having a blood alcohol concentration of

• .08% or greater for DUI per se or
• .02% or greater for UDD,

witness testimony can sometimes cast doubts on the accuracy of the test results.

19. No Impairment

If you were charged with DUI or DWAI based on actual impairment (rather than your BAC level), it is not enough for the prosecution to prove that you

• drank alcohol or
• used drugs.

The prosecutor must prove beyond a reasonable doubt that your driving was actually negatively affected by alcohol or drugs. This can be difficult if your BAC is within the legal range.

20. You Were Not Driving

Finally, if you did not actually drive, you cannot be guilty of DUI, DWAI or UDD. This may seem obvious, but sometimes police arrest you because:

• You are found sitting in your car inebriated (“sleeping it off”),
• You are found at the scene of a car accident,
• You are trying to get into a vehicle when you are drunk, or
• Your car has been left at the side of the road somewhere.

Though if no one actually saw you driving, it can be difficult for the prosecutor to prove you actually drove drunk. In such a case the “no driving” defense can be effective.

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Legal References