How Can You Challenge Evidence in a DWI Case?
Facing a DWI charge can be scary, but it's important to remember that evidence presented by the prosecution isn’t always infallible. From the initial traffic stop to chemical tests and officer observations, each piece of evidence must adhere to strict legal standards. Challenging the validity of this evidence is a critical strategy in defending against DWI charges.
A DWI lawyer can scrutinize the procedures followed during your arrest, identify any violations of your rights, and contest the admissibility of questionable evidence. With offices in Raymore, Missouri, and Harrisonville, Missouri, Friedrich Law Offices, P.C. understands that the avenues available to challenge DWI evidence can impact the outcome of your case, and we want to help.
We’ve collected a list of the knowledge someone who has been charged with DWI should have, so that you and your lawyer can be ready for your defense.
Questioning the Legality of the Traffic Stop
The first line of defense in any DWI case is often the initial stop. Under Missouri law, an officer must have a legitimate reason—known as “reasonable suspicion”—to stop your vehicle. This could include swerving, speeding, running a red light, or even a broken taillight. If no clear violation of law occurred, your constitutional rights may have been infringed.
A seasoned DWI lawyer can find out if the officer had a legal justification for pulling you over. They may request dashcam footage or interview witnesses to challenge the legality of the stop. If it’s proven that the stop was unlawful, any evidence obtained afterward—such as breath tests or confessions—could be thrown out.
Scrutinizing Field Sobriety Tests
Field sobriety tests (FSTs) are commonly used during DWI stops to assess a driver’s coordination and cognitive function. These tests often include the horizontal gaze nystagmus (eye test), the Walk-and-Turn, and the One-Leg Stand. However, these tests can be highly subjective and prone to error.
Many factors can impact your performance on these tests that have nothing to do with alcohol, such as uneven pavement, nervousness, or even certain medical conditions like vertigo or arthritis. A qualified DWI lawyer will analyze how the tests were conducted, whether the officer was properly trained, and if video evidence contradicts the officer’s notes.
Additionally, the National Highway Traffic Safety Administration (NHTSA) has strict guidelines for administering FSTs. If the officer failed to follow these protocols, the results may be deemed unreliable in court.
Challenging Chemical Test Results
Chemical testing is often central to the prosecution’s case in a DWI charge. This includes breath, blood, or urine tests used to determine blood alcohol concentration (BAC). Missouri has an “implied consent” law, meaning that refusing to submit to a chemical test can result in license suspension. However, even if you comply, the test results aren’t automatically infallible.
Several issues can arise with chemical testing:
Improper calibration of the breathalyzer device
Inadequate training of the test operator
Contaminated or mislabeled samples
Time delays between the stop and testing
Medical conditions such as acid reflux or diabetes that may skew results
Your lawyer can review maintenance logs, testing protocols, and health records to build a case against the validity of your BAC reading. In many cases, even a slight deviation from proper procedure can be enough to suppress the results in court.
Examining Officer Observations
Officer observations, such as slurred speech, glassy eyes, or the odor of alcohol, are often cited in DWI arrest reports. While these may sound convincing on paper, they’re highly subjective and susceptible to misinterpretation. For example, red eyes could be the result of allergies or fatigue, and slurred speech may stem from anxiety or a speech impediment.
A DWI lawyer will work to cast doubt on these observations, especially if they conflict with objective evidence like video recordings or witness testimony. The goal is to challenge the credibility of the officer’s account and offer plausible alternative explanations for your behavior.
Investigating Procedural Errors
The law mandates that officers follow strict guidelines when conducting a DWI arrest. Any deviation from these procedures could be grounds to suppress evidence. Examples include failing to read your Miranda rights, improperly documenting the arrest, or conducting searches without a warrant or consent.
Procedural errors might seem minor, but in the eyes of the court, they can have major consequences. If these mistakes are serious enough, they can lead to reduced charges or even full dismissal.
For instance, if it’s shown that your arrest wasn’t based on probable cause or that evidence was obtained in violation of your Fourth Amendment rights, the entire case could fall apart.
Filing Motions to Suppress Evidence
A critical component of DWI defense in Missouri involves filing pretrial motions to suppress improperly obtained evidence. These motions argue that certain key evidence—such as a failed breathalyzer test or incriminating statement—was collected in a way that violated your constitutional rights.
Your DWI lawyer will prepare and present these motions at a suppression hearing, where the judge determines whether the evidence in question should be excluded. If a motion to suppress is granted, the prosecution may no longer have enough evidence to continue pursuing the DWI charge, leading to favorable outcomes for the defendant.
Leveraging Expert Witnesses
Expert witnesses can be invaluable in undermining the prosecution’s narrative. These individuals often possess specialized knowledge in areas such as toxicology, forensic science, and chemical testing procedures.
A knowledgeable lawyer will work with experts to highlight flaws in the prosecution’s evidence and to offer scientifically backed alternative explanations. The presence of expert testimony can not only influence a judge’s ruling but also create reasonable doubt for a jury.
Such expert knowledge can expose the details and potential inaccuracies of DWI testing in ways that are compelling and easy to understand in court.
Exploring Alternative Explanations
Not every sign of impaired driving is due to alcohol or drug use. Lawyers explore all potential alternative explanations that could account for your behavior or appearance during the arrest.
These may include:
Lack of sleep or fatigue
Emotional distress
Side effects from prescribed medication
Chronic health issues like diabetes or neurological conditions
By providing a legitimate, non-alcohol-related reason for any symptoms observed by the officer, a DWI lawyer can raise doubt about whether you were truly impaired at the time of the stop.
Reviewing Video Evidence
In recent years, the use of dashcams and body-worn cameras has become widespread in Missouri law enforcement. These videos are often key pieces of evidence in DWI cases. While they can support the officer’s account, they can also contradict it, which opens the door to a robust defense.
A DWI lawyer will thoroughly review all available video footage to identify inconsistencies between the officer’s written report and what actually occurred during the stop. For example, the officer might claim the driver was staggering, but the video may show the individual walking steadily.
These visual records can provide powerful, objective evidence to challenge subjective claims and discredit unreliable testimony.
Assessing the Chain of Custody
The “chain of custody” refers to the documentation that tracks how evidence is handled, from the time it’s collected until it’s presented in court. Any break in this chain could result in the contamination or misidentification of evidence, making it inadmissible.
For instance, if a blood sample wasn’t properly labeled or was stored in the wrong conditions, it may no longer be considered reliable. A DWI lawyer will review these logs to detect mishandling, delays, or storage issues that could compromise the integrity of the sample.
Inaccurate or missing documentation regarding the handling of evidence can significantly weaken the prosecution’s case and potentially lead to its dismissal.
Contact Us Today
Challenging evidence in a DWI case requires deep legal knowledge and attention to detail. From traffic stop legality to testing procedures, there are many opportunities to weaken the prosecution’s claims. If you’re facing a DWI charge in Raymore, Harrisonville, or Butler, Missouri, contact Friedrich Law Office, P.C. for experienced legal representation and personalized guidance every step of the way. Call us today.