5 Police Mistakes That Can Affect Your Wisconsin OWI Case

Police officers are expected to follow strict constitutional and procedural rules when investigating suspected drunk driving. Yet in reality, corners are cut and errors are made every day—often without the driver even realizing it.

The difference between a conviction and a dismissal can come down to whether these mistakes are identified and leveraged correctly.

That’s where an experienced defense attorney makes all the difference. Lawyers trained in OWI defense know exactly how to spot errors, document them, and turn them into legal arguments that can suppress damaging evidence or dismantle the prosecution’s case entirely.

Here are five of the most common police mistakes in Wisconsin OWI cases—and why having the right lawyer is essential to making them work for you.

Don’t let a police error go unchallenged. The right defense could mean the difference between conviction and freedom. Contact Attorney Patrick Stangl today for a free consultation.

1. Unlawful Traffic Stop or Arrest

An officer cannot legally stop your vehicle without “reasonable suspicion” of a violation, nor can they arrest you without “probable cause.” If either standard is missing, your constitutional rights are violated.

How an OWI attorney can help: An attorney can file a motion to suppress, asking the court to exclude all evidence that came from the unlawful stop or arrest. Without that evidence, the prosecution often has no case left to pursue. Many OWI charges have been dismissed entirely because a lawyer successfully proved the stop or arrest was unconstitutional.

Attorney Stangl won three recent jury acquittals in a row on OWI-PAC first offense cases despite elevated BAC results (.12, .15, and .20)—demonstrating his readiness to fight and ability to dismantle cases, even when evidence seems stacked against clients.

2. Improperly Administered Field Sobriety or Breath Test

Field Sobriety Tests (FSTs) and breath tests are governed by strict NHTSA protocols. Officers often misstate instructions, overlook medical conditions, or conduct tests in poor conditions (uneven pavement, flashing lights, bad weather).

Even minor mistakes can invalidate the results.

How an OWI attorney can help: An experienced OWI attorney can dissect the circumstances of your test, compare them against the official guidelines, and highlight every deviation. By showing that the test wasn’t administered properly—or that the environment tainted the results—your lawyer can challenge the accuracy of the evidence and undermine the state’s case against you.

In a particularly challenging case involving a high BAC and an off-duty law enforcement officer, Attorney Stangl exposed improper charging and procedural flaws that led to a mistrial.

3. Incomplete or Inaccurate Police Reports

In Wisconsin, officers are required to write detailed and accurate reports after each investigation and arrest. Depending on the officer and/or the situation, it’s not uncommon for officers to skip taking notes, which can lead to incomplete or inaccurate reports.

There could be a glaring inconsistency between the officer’s report and testimony. They might have failed to check boxes. There may be an indication in the report that demonstrates the officer is making overstated claims.

These errors may not seem significant on their own, but in court they can reveal serious credibility issues.

How an OWI attorney can help: Defense attorneys carefully compare police reports to testimony, video footage, and other records. When contradictions appear, a lawyer can highlight them to cast doubt on the officer’s reliability in front of a judge or jury. Discrediting the officer’s version of events can be a powerful tool for reducing or dismissing charges.

Attorney Stangl's consistent jury victories in OWI cases where the prosecution’s chemical tests seemed convincing demonstrate his skill in undercutting officer testimony and written reports.

4. Stops Based Solely on Anonymous Tips

An anonymous tip alone isn’t enough to justify a stop. Without the officer personally observing suspicious driving, the stop may be unconstitutional.

How an OWI attorney can help: An attorney can challenge the legality of the stop, arguing that any evidence gathered afterward must be suppressed. If successful, this can gut the prosecution’s case. Courts have repeatedly ruled in favor of drivers where lawyers proved police relied solely on an anonymous call without their own observations.

5. Law Enforcement Showing Up Unprepared for Hearings

Officers sometimes underestimate the importance of pretrial hearings, showing up without reports, notes, or a clear memory of the incident. These hearings often determine what evidence will be allowed at trial.

How an OWI attorney can help: A skilled OWI lawyer knows how to capitalize on an unprepared officer—pressing them with detailed questions, exposing gaps in memory, and locking in testimony that undermines the state’s case. In some instances, cases have been dismissed at this stage before the trial even begins.

Attorney Stangl recently won three consecutive OWI 5th/6th offense victories:

• Case 1: Prior conviction invalidated due to improper waiver of counsel.

• Case 2: Lack of probable cause led to dismissal.

• Case 3: Prosecution dropped charges after the officer’s false testimony about FSTs,

Why Legal Expertise Makes All the Difference

OWI convictions in Wisconsin carry serious consequences—jail time, license suspension, ignition interlock, criminal records. But when police make mistakes, you have leverage. 

It’s one thing to know an officer messed up. It’s another to strategically challenge that mistake, using rigorous legal knowledge, procedural acumen, and courtroom artistry. Attorney Stangl brings all three—and a proven record of success.

The sooner you involve a skilled defense attorney like Pat Stangl, the faster these errors can be identified and used to your advantage.

What to do if You've Been Arrested and Charged with OWI in Wisconsin

If you are facing OWI, DWI, DUI, BAC or PAC charges in Wisconsin, you should contact a skilled criminal defense attorney to assist in your defense as soon as possible.

Attorney Patrick Stangl explains why you should never give up hope when fighting repeat DUI/OWI charges in Wisconsin:

Criminal Defense Lawyer Patrick J. Stangl has been aggressively fighting to protect the rights of drivers accused of OWI and other drunk driving charges for over 30 years. He remains committed to protecting the innocent against OWI charges in Madison, Hayward and across Wisconsin.