Blood Alcohol Concentration Testing

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Posted by Christopher Combs on

Blood alcohol concentration testing in Missouri. While many people assume that having a blood alcohol content of .08% or higher automatically means they’ll be hit with a DWI charge and conviction. But, that isn’t always the case. Combs Waterkotte consists of dedicated and skilled criminal defense attorneys with extensive experience challenging the results of both Breathalyzers and blood tests. If you’re facing a DWI charge, we will zealously defend your rights under the law, and have any unreliable evidence called into question, if not thrown out of court.

A DWI conviction can have serious repercussions for your reputation and freedom, but the state still has the burden of proving the charges against you. If the evidence is questionable, we’ll work to have your charges reduced or dismissed, and are ready to go to trial for a not guilty-verdict if we have to. Call Combs Waterkotte today at (314) 900-HELP or contact us online for a free consultation.

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When Can a Police Officer Order a Blood Alcohol Concentration Test in St. Louis, Missouri?

A police officer may request a blood alcohol concentration test if:

  • They have reasonable grounds to believe you were operating a motor vehicle while intoxicated (RSMo. 302.574)
  • They have reasonable grounds to believe that, if you were under 21, were operating a motor vehicle with more than .02% BAC (RSMo. 302.574)
  • You were involved in a motor vehicle accident (RSMo. 577.021)

Can I Refuse a BAC Test in Missouri

Under Missouri Revised Statute §577.020, any person operating a vehicle has given “implied consent” to chemical testing of alcohol. Meaning, simply having a driver’s license and driving a vehicle, you’ve agreed to undergo a chemical test.

You can still refuse the test (the officer can’t physically force you), but that will result in a “Chemical Revocation” of your license for one year. You can appeal the decision to the Circuit or Associate Circuit Court in the country where the stop occurred within 30 days of the revocation. In the appeal, you and your St. Louis, MO DWI lawyer can argue the officer lacked “reasonable grounds” to require the blood alcohol concentration test. However, the evidence against you will be a report the officer makes under penalty of perjury, which will carry a lot of weight with the judge.

While there are stiff consequences for refusing a blood alcohol concentration test, if you blow more than a .08% BAC you would be considered guilty of a DWI per se. Meaning, no other evidence is needed to convict you of a DWI.

If you aren’t drunk or on drugs, it’s foolish to refuse a blood alcohol content test. If you have been drinking, refusing the test, either in the field or at the station after an arrest, allows you to fight a charge that is only based on an officer’s testimony. However, your refusal can also be used against you in court.

If it’s your first DWI offense, your license would only be revoked for 90 days, but you would have a conviction on your record.

If you are arrested for a DWI, you will be read the implied consent law. You then have 20 minutes to request a lawyer. Always do so. They’ll know whether or not you should submit to a blood alcohol test at the police station.

Can I Still Be Arrested If I Pass a Blood Alcohol Test in St. Louis, MO?

Yes, you can still be arrested on suspicion of a DWI if you blow under a .08% in the field. If dash cam video shows you driving erratically, or you fail your field sobriety test, an officer may still have probable cause to arrest you, although the charges will be easier to fight.

If an officer suspects you are not drunk, but committed DWI with drugs, they can still arrest you and get a warrant for a blood or urine test.

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Can You Fight a Blood Alcohol Concentration Test in St. Louis and Missouri Court?

There are several ways to challenge your blood alcohol concentration testing results in court in St. Louis, MO, but you’ll need an experienced and aggressive DWI lawyer to do it. The defense strategy will depend on whether your BAC of over .08% was taken by a Breathalyzer in the field, or a blood sample taken after your arrest.


Breathalyzers are used to confirm a police officer’s suspicions and offer reasonable grounds for an arrest. However, they are not as accurate as many people believe them to be. According to a peer-reviewed study by LaBianca, Simpson, Thompson, Breathalyzers have a margin of error of 50% when compared to an actual blood test. That means, a reading of .1% could indicate an actual BAC of anywhere between .05% and .15%.

Breathalyzers determine your BAC by measuring the amount of ethyl alcohol in your breath sample. However, there are numerous molecules with similar structures in human breath, including acetone. Dieters and diabetics may have increased levels of acetone, leading to a false reading. Misreadings can also be given because of:

  • Interference from cell phones or the officer’s radio
  • Recently ingested bread
  • Tobacco use
  • Improper calibration

While Breathalyzer results are admissible in court, they are not considered irrefutable evidence in Missouri. If your Breathalyzer results hover around the legal limit, we can argue that the margin of error is too great to be reliable, and the results are not sufficient for proof beyond a reasonable doubt.

In order to be reliable, a Breathalyzer should only read alcohol vapors coming from a person’s lungs, and not their mouth. If you just had one or two beers, there may be alcohol in your mouth that causes your BAC to read as much higher than it actually is. For that reason, officers are supposed to observe a suspect for 15 to 20 minutes before administering a test. If they didn’t follow proper procedure, we can work to prevent the test from being entered as evidence.

Blood Test

Whether you took a Breathalyzer or blew over the limit or not, after an arrest you will be asked to give a blood sample to check your system for alcohol and/or other drugs. While the BAC readings may be more reliable, there are still ways that a defense attorney can challenge the evidence in St. Louis, Missouri court:

  • Rising Blood Alcohol” — Everyone metabolizes alcohol at different rates. After ingesting alcohol, your BAC can continue to rise for anywhere from 30 minutes to 3 hours. So, if there was a significant delay between when you were pulled over and when the blood test occurred, you and your St. Louis, MO DWI lawyer can argue the results don’t indicate your BAC at the time you were driving.
  • Improper Handling and Preservation — Taking a blood sample is a medical procedure. Like any other medical test, it has to be performed, tested, transported and stored correctly. If there were errors made when the test was administered or with how the sample was handled, the sample may ferment, leading to an inaccurately high reading.
  • Warrantless Blood Tests — Implied consent allows police to take a blood sample from you if you are unconscious. If you’re conscious, police are allowed to take a blood sample if you refuse, but only if they get a warrant from a judge. Otherwise, the Supreme Court has ruled that it would violate your Fourth Amendment rights against unreasonable search and seizure. If they forced you to give a sample, after you refused and without a warrant, the results can be thrown out.

Our St. Louis, MO DWI defense lawyers are experienced and diligent, and pursue every legal avenue to get you the best possible results in your case. We will develop a strong defense strategy in your case and work to have your charges dismissed or reduced.

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Call a Blood Alcohol Concentration Testing Lawyer in St. Louis, Missouri Today

Being charged with a DWI is stressful and frightening for anyone. But you still have your right to due process under the law. Combs Waterkotte’s criminal defense lawyers are fearless in the courtroom, and know how to investigate cases and demonstrate where the state’s evidence is weak. If you’re facing DWI charges in St. Louis, MO, speak to a blood alcohol concentration testing lawyer today at (314) 900-HELP or contact us online.