What the State Has to Prove in a DWI Case
To secure a conviction for DWI under RSMo 577.010, Missouri prosecutors must establish several elements beyond a reasonable doubt:
- You operated a motor vehicle
- You did so while under the influence of alcohol or drugs, or both
- This impairment affected your ability to drive safely
Additionally, under RSMo 577.012, prosecutors may pursue a “per se” DWI, depending on the level of your blood alcohol concentration. Normal drivers are held to a 0.08% limit, commercial drivers are held at 0.04%, and drivers younger than 21 are held at 0.02%.
What is the Burden of Proof in a DWI Case?
The prosecution has the “burden of proof” to show that you were undeniably under the influence of drugs or alcohol when you were stopped or arrested. Their job is not to simply prove that you consumed or used drugs before you got behind the wheel. They need to show that the substances irrefutably affected your ability to drive.
A positive breath or blood test alone does not automatically establish guilt, because the science behind alcohol detection and its correlation to actual driving impairment can be challenged. Defense attorneys often work with toxicologists and experts to undermine the state’s reliance on test results and other evidence.
When prosecutors cannot meet their burden, cases are dismissed or reduced. This is why examining every element of the state’s case is so critical.
Possible Defense Strategies for DWIs in St. Louis
DWI defenses fall into several categories, each attacking a different part of the government’s case. Each criminal case is unique. The circumstances surrounding your arrest might be different from another person’s DWI charges. However, these defenses offer a starting point your defense attorney can explore as you fight to protect your freedoms.
Was the Traffic Stop Valid? Was There Probable Cause?
Law enforcement cannot simply pull over a vehicle on suspicion alone. Under the Fourth Amendment, officers must observe specific conduct that violates a traffic law or reasonably suggests impairment. Common traffic violations that might justify a stop include swerving between lanes, straddling lane lines, erratic acceleration, failure to maintain speed, or equipment failures like a broken taillight.
If the officer lacked reasonable suspicion to initiate the stop, everything that happened led to your arrest could be suppressed: field sobriety tests, breath tests, blood draws, and any statements you made under the “fruit of the poisonous tree” doctrine. Under this Fourth Amendment principle, evidence obtained in violation of your constitutional rights cannot be used against you, even if it would otherwise prove guilt.
Your defense attorney can argue that because the traffic stop never should have happened, the related charge and arrest also should not have happened. It’s possible to have your DWI dismissed because the prosecution’s best evidence has been suppressed. To help fight your charge, we examine dashcam footage, body-camera recordings, the officer’s written notes, and radio dispatch recordings to determine whether the officer actually had reasonable suspicion. If the officer’s stated reason for the stop does not match the video evidence, that is a powerful tool.
Was Breath Test Result Accurate?
Breath-testing machines such as Intoxilyzers and Alco-Sensors are not infallible instruments. They require proper maintenance, regular calibration, and current certification to produce reliable results. If records show the machine was not serviced on schedule, or if certification documentation is missing or expired, we can argue that the test result is unreliable and challenge its accuracy.
Additionally, “mouth alcohol” can artificially inflate breath-test results. If you burped, hiccupped, or had residual alcohol in your mouth from mouthwash, cough syrup, or certain foods at the time of testing, the breathalyzer may significantly overestimate your actual blood alcohol content. Radio frequency interference (RFI) from nearby radio transmission towers or cell phone networks can also distort readings, particularly in areas near airports or police dispatch facilities.
We obtain the machine’s complete maintenance records, calibration logs, and the operator’s certification status. We investigate whether any mouth alcohol, testing procedures violations, or environmental interference could have affected the result. Expert testimony on breathalyzer reliability is often key to challenging these results.
Were Field Sobriety Tests Held Properly?
The three standardized field sobriety tests (Horizontal Gaze Nystagmus, One-Leg Stand, Walk-and-Turn) are subjective and prone to error. Poor lighting, uneven pavement, footwear, medical conditions, fatigue, and anxiety can all produce “failed” performance despite sobriety.
Studies show the tests are not as reliable as law enforcement claims, especially in real-world conditions outside a laboratory. A person’s performance depends on age, balance, coordination, and understanding of instructions, none of which correlate perfectly to actual impairment. Additionally, some people fail these tests while completely sober due to naturally poor balance or nervousness during the encounter.
We hire experts to challenge SFST administration and interpretation, and we highlight any deviations from standardized procedure that the officer committed.
We Contest Prior Convictions Used for Felony Tier Enhancement
Under RSMo 577.023, DWI charges escalate to felony tier when aggravating factors are present, including prior DWI convictions. However, prior convictions must be valid to count. If a prior was obtained without adequate legal counsel, if the defendant did not knowingly waive rights, or if the prior occurred in another state with different standards, challenges to its validity may reduce the current charge from felony to misdemeanor.
We examine the records of prior convictions and file motions to challenge their constitutional validity if warranted.
Why Choose Brian J. Cooke
A DWI charge is a serious situation that demands immediate, expert attention. Brian J. Cooke has spent his career defending people facing DWI charges in and around St. Louis. He understands the science behind breath testing, the procedures law enforcement must follow, and the case law that protects your rights. He is committed to helping good people stuck in bad situations navigate the criminal justice system.
Every case is different. Some are best resolved through negotiation with prosecutors; others require aggressive courtroom litigation. Brian will evaluate your case, explain your options clearly, and fight for the best possible outcome. That might mean dismissal of the charges, reduction to a lesser offense, or a successful trial defense.
FAQs about Challenging DWIs
Can I beat a DWI charge?
Yes, many DWI cases are dismissed or reduced. Defenses may focus on the traffic stop, the breath or blood test, field sobriety tests, or the officer’s observations. Success depends on the specific facts and evidence in your case.
What is the burden of proof in a DWI case?
The prosecution must prove guilt beyond a reasonable doubt. That is a high standard. The defendant does not have to prove innocence; the state must prove guilt. Many prosecutors do not meet that standard.
Do I need a lawyer for a DWI charge?
Yes. DWI law is complex, and the stakes are high. A conviction carries license suspension, fines, possible jail time, and long-term employment and insurance consequences. An experienced DWI attorney can identify defenses, negotiate with prosecutors, and protect your rights.
How long does a DWI case take?
It varies. Some cases are resolved quickly through negotiation. Others require motions, discovery disputes, expert witness work, and trial. A case may take weeks to months. The complexity of your case and court scheduling determine the timeline.
Call a DWI Defense Lawyer Now
If you or a loved one have been charged with a DWI, you should not wait to start your defense. The prosecution has the advantage. Finding a defense attorney who understands how they approach DWIs and the possible challenges you can raise against the state’s case is crucial. Contact Attorney Brian J. Cooke to review your case. He can examine the facts, explain your rights, and develop a strategy tailored to your situation. Call (314) 526-3779 to schedule your free consultation.
