Missouri Boating While Intoxicated Defense Attorney

Quick Reference — § 577.013 Boating While Intoxicated

What Is BWI Under Missouri Law?

Under § 577.013, a person commits boating while intoxicated when they operate a vessel while in an intoxicated condition.³ The statute mirrors § 577.010 (DWI) in virtually every respect — same elements, same mental state requirement, same classification structure.

“Vessel” includes motorboats, sailboats, personal watercraft (jet skis), and other watercraft. The intoxication standard is the same: impairment by alcohol, drugs, or any combination.⁴

BWI Counts as a DWI Prior — and Vice Versa

This is the most important thing to understand about BWI charges. A BWI conviction counts as an “intoxication-related traffic offense” under § 577.001 — which means it counts as a prior for future DWI charges, and prior DWI convictions count toward BWI offense escalation.⁵

A person with one DWI conviction who is then convicted of BWI within 5 years is a “prior offender” — Class A Misdemeanor with mandatory minimum jail time. The two types of offenses are treated identically for enhancement purposes.

Elements of the Offense

The prosecution must prove:

1. The person operated a vessel — meaning physically controlled or operated a boat, jet ski, or other watercraft.⁶

2. The person was in an intoxicated condition — impaired by alcohol, drugs, or a combination.⁷

3. The vessel was operated on the waters of this state.

Each element can be challenged. The “operation” element is frequently contested in BWI cases — anchored boats, docked vessels, and situations where someone else was actually piloting the craft all present defense opportunities.

How BWI Cases Differ from DWI Cases

While the penalties are identical, the investigation and evidence collection in BWI cases differ in ways that create unique defense opportunities:

No Traffic Violation Required

On the water, there are no lane markings, speed limit signs (in most areas), or traffic signals. Missouri Water Patrol officers often initiate contact through “safety checks” — stopping vessels to check for life jackets, registration, and fire extinguishers. The constitutional basis for these stops is different from traffic stops on roads, and the legal standards may present challenges.⁸

Environmental Factors

Sun exposure, heat, dehydration, fatigue from swimming or physical activity, and motion from waves can all mimic signs of intoxication. These factors can explain observations like unsteady balance, flushed skin, slurred speech, and bloodshot eyes — all of which officers may attribute to alcohol impairment.

Field Sobriety Tests on Water

Standard SFSTs were designed for solid ground. Administering balance-based tests on a rocking boat or uneven dock fundamentally compromises their reliability. Officers sometimes administer modified tests, but these lack the standardized validation of NHTSA-approved SFSTs.

Delayed Testing

BAC testing in BWI cases often occurs much later than in traffic DWI cases — after the boat is brought to shore, the person is transported to a testing facility, and the process is completed. This longer delay strengthens the rising BAC defense.

Defense Strategies

Challenge the Stop

If the initial contact with the vessel was not based on a valid safety check protocol or articulable reasonable suspicion, the stop itself may be unconstitutional.

Challenge the Observations

Environmental factors — sun, heat, waves, physical exertion — provide strong alternative explanations for the physical indicators officers rely on to establish impairment on the water.

Challenge Field Sobriety Tests

SFSTs performed on boats, docks, or at the shore lack the controlled conditions required for reliable results. We challenge both the administration and the interpretation of these tests.

Challenge BAC Evidence

All standard BAC challenges apply — calibration, operator certification, observation period, chain of custody — with the additional factor that longer delays between operation and testing strengthen the rising BAC defense.

Challenge “Operation”

If the person was not actually operating the vessel — a passenger, an anchor was dropped, someone else was at the controls — the operation element fails.

Related Charges

Driving While Intoxicated (§ 577.010)

BWI and DWI share identical classification and penalty structures. A BWI conviction counts as a prior for future DWI cases.

Driving with Excessive BAC (§ 577.012)

The per se BAC offense also has a boating equivalent — operating a vessel with BAC ≥ 0.08%.

Minor in Possession / Abuse and Lose (§ 577.500)

Persons under 21 face the lower 0.02% threshold on the water, with the same license consequences as underage DWI.

Facing BWI Charges in St. Louis?

BWI cases are prosecuted with the same seriousness as DWI — because the law treats them identically. But the unique circumstances of on-the-water enforcement create defense opportunities that don’t exist in typical traffic DWI cases. Environmental factors, delayed testing, non-standard field sobriety tests, and questionable stop procedures all create openings that we know how to exploit.

Call us 24/7 for a free consultation. The defense starts with a conversation.

References

1. § 577.013, RSMo [BWI — same classification structure as § 577.010].
2. § 302.505, RSMo [Administrative license action applies to BWI].
3. § 577.013.1, RSMo [Elements of BWI].
4. § 577.001, RSMo [Definitions applicable to BWI].
5. § 577.001.9, RSMo [BWI included in “intoxication-related traffic offense” definition].
6. § 577.013.1, RSMo.
7. § 577.001.12, RSMo [Definition of “intoxicated condition”].
8. See U.S. v. Villamonte-Marquez, 462 U.S. 579 (1983) [Regulatory stops of vessels].