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. The 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. Colorado DUI breath testing procedures weren’t correctly followed
• 2. Colorado DUI breath testing errors
• 3. DUI breath tests and residual mouth alcohol
• 4. Your diet or medical condition led to a false BAC result 
  • 4.1. GERD, acid reflux, or heartburn
  • 4.2. High protein diets
  • 4.3. Diabetes (hyperglycemia) or hypoglycemia
• 5. Your partition ratio differs from the DUI breath testing norms
• 6. Colorado DUI blood testing procedures weren’t correctly followed
• 7. Inconsistent results from independent testing of your blood
• 8. DUI blood testing errors
• 9. “Rising blood alcohol”
• 10. There was no lawful reason for your traffic stop
• 11. The officer didn’t advise you of your Miranda rights
• 12. Drug testing without probable cause
• 13. Your blood was illegally obtained through an involuntary blood test
• 14. There are other explanations for your physical symptoms
• 15. There was another reason for your bad driving
• 16. Colorado field sobriety tests (“FSTs”) often aren’t accurate
• 17. Unconstitutional Colorado sobriety checkpoint
• 18. Inconsistent witness testimony
• 19. Your driving wasn’t impaired
• 20. You weren’t driving

1. Colorado DUI breath testing procedures weren’t correctly followed

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

Keep in mind that under section 42-4-1301(1)(f) of the Colorado Revised Statutes (C.R.S.), 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. Colorado DUI breath testing errors

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. DUI breath tests and residual mouth alcohol

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

Residual mouth alcohol can taint the results of a Colorado 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 Colorado EBAT operator must observe you continuously for 20 minutes before beginning the test. If this time period isn’t 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. Your diet or medical condition led to a false BAC result

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

4.1. GERD, acid reflux, or heartburn

In these conditions, stomach contents can back up into the esophagus. When you take a DUI 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 Colorado EBAT.

4.2. 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 the body doesn’t 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.

But “burning” fat for energy produces a waste product known as ketones. When eliminated from the 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

4.3. Diabetes (hyperglycemia) or hypoglycemia

Once the carbohydrates we eat are broken down into sugars, glucose normally enters our bloodstreams from the small intestine. The pancreas then releases the hormone insulin to help deliver the glucose to our muscles and organs.

But in people with diabetes (hyperglycemia) the 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, the body can’t metabolize glucose for fuel. It has to use fat, which is broken down in the liver.⁵

But when the 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 the 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. Your partition ratio differs from DUI breath testing norms

Colorado DUI breath tests do not measure blood alcohol directly.

When we drink, some of the alcohol in our blood passes through

• the membranes of our capillaries and
• into our lungs.

This is the alcohol measured during an EBAT. The machine then mathematically converts this to a blood alcohol equivalent.

However, not everyone’s lungs absorb alcohol from the blood at the same rate. Colorado uses 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.

But your actual partition ratio may differ – not just in general, but because of when and where the test is taken. 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.

In Colorado, you can present evidence of partition ratio variations to the jury. So an expert witness who understands the science of DUI breath tests and can explain them clearly can make a huge difference in the outcome of your case, 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. Failure to comply with Colorado DUI blood testing procedures

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.

Colorado 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 results from independent testing of your blood

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 Colorado DUI blood test over a DUI breath test.

8. DUI blood testing errors

DUI blood tests are considered fairly accurate. But they are not foolproof.

Sometimes, even when everything is done right, blood samples go bad. Ways a Colorado 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 isn’t 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.

As a result, even if you drink enough to get drunk, you won’t be drunk immediately. So if you are pulled over shortly after drinking, you might be perfectly capable of driving.

But your BAC would still be rising. By the time of your evidentiary Colorado 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.

The prosecutor will always argue that your BAC at the time of the test “proves” you were under the influence of, or had your ability impaired by, alcohol. But like all the best DUI lawyers, we know that isn’t always the case.

A skilled DUI defense attorney and DUI expert witness 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. There was no lawful reason for your 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).

This is just one reason why it is so important to retain an experienced Colorado DUI defense lawyer right away if you are charged with

• DUI,
• DUI per se,
• DWAI or
• UDD.

11. The officer didn’t advise you of your Miranda rights

Despite what you might have seen on TV cop shows, 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.

A “custodial interrogation” occurs when an officer asks you questions designed to solicit incriminating responses after being arrested.

If these conditions have been satisfied, the officer must advise you of your Miranda rights. Any statements you make when such a warning hasn’t 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.

But 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. Drug testing without probable cause

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

• DUI breath test and
• DUI 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. Your blood was illegally obtained through an involuntary blood test

CRS 42-4-1301(1)(e) and 42-4-1301.1(3) provide limited circumstances in which results of an involuntary blood test are admissible in Colorado to prove you guilty of

• DUI,
• DUI per se,
• DWAI or
• UDD.

Your blood can only be taken against your will in Colorado when the officer has probable cause to believe that you have committed:

14. There are other explanations for your physical symptoms

Indirect evidence of intoxication often comes from the arresting officer testifying 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 don’t necessarily mean you were intoxicated. Innocent reasons for these signs might include:

• you were tired,
• you had allergies,
• you were dehydrated,
• you’d 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. There was another reason for your bad driving

While the police like to think that all bad drivers must be DUI, we know this isn’t 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 aren’t the only explanation for bad driving. Sober people drive badly, too.

If you do any of the above, you may receive a ticket. But you shouldn’t be labeled a drunk driver.

16. Colorado field sobriety tests (“FSTs”) often aren’t accurate

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.

And even when performed under ideal conditions, Colorado field sobriety tests aren’t completely accurate indicators of alcohol and/or drug impairment.¹⁰ In particular, as BAC levels fall, FSTs become less and 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. Unconstitutional Colorado sobriety checkpoint

Normally police in Colorado must have probable cause to stop and question a motorist. This means observing either:

• a traffic violation,
• a defect in the vehicle that affects safety, or
• a driving pattern that indicates the driver 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.

Failure to comply with one of these guidelines does not automatically make a sobriety checkpoint illegal. It is a factor the court may consider, however. And if there are multiple violations, the roadblock may have violated your constitutional rights. 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).
• No convenient reasonable procedures for DUI breath testing.
• No drug recognition expert (DRE) to determine whether drugs other than alcohol were involved.
• Inadequate briefing of the supervising officers.
• Inadequate publicity to notify drivers of upcoming DUI sobriety checks.

18. Inconsistent witness testimony

The law enforcement officer who arrested you isn’t 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. Your driving wasn’t impaired

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.

This is particularly important in cases of DUI of drugs or DWAI – cases in which your BAC is below Colorado’s “legal” limit of .08% for DUI per se.

20. You weren’t driving

Finally, if you didn’t actually drive, you can’t be guilty of DUI, DWAI or UDD. This may seem obvious, but sometimes police arrest someone because:

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

But 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 quite effective.

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

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Legal references

1. See 5 CCR 1005-2.
2. 42-4-1301.1 (1)(a)(3), C.R.S.
3. See Lawrence Taylor, Drunk Driving Defense 3d Edition, page 685. (“…the likelihood exists of auto-generated isopropyl alcohol upon the introduction of carbohydrates in the presence of ketosis and that the Intoxilyzer [DUI breath testing instrument] cannot dependably distinguish ethanol from isopropyl alcohol.”)
4. See Mayo Clinic, Types of diabetes: What are the differences?
5. American Diabetes Association, Hyperglycemia (High blood glucose).
6. University of San Francisco, What are ketones and why do I need to know about them?
7. American Diabetes Association.
8. DKA (Ketoacidosis) & Ketones
9. 42-4-1301.1.(2)(b)(I), C.R.S.
10. See U.S. Department of Transportation “DWI Detection and Standardized Field Sobriety Testing NHTSA Student Manual, March 2013 edition.
11. See Michigan Department of State Police v. Sitz, 496 US 444 (1990).