REASONABLE CAUSE IN THE BUI ARENA 

Written by: Hearing Office Staff

Often we see angst over whether a boarding officer had reasonable 

cause to direct a chemical test in a potential boating under the 

influence (BUI) violation. So we thought we would generally 

reiterate the laws, regulations, and definitions.

Where’s the law? See 46 USC 2302(c) Where’s the regulations? See 

33 CFR part 95.

What’s required for a BUI? A person operating a vessel while 

impaired or intoxicated by a drug or alcohol. 

What’s operating? Having an essential role in the operation or 

control of a recreational vessel underway, or in the matter of a 

commercial vessel be a crewmember, pilot, or watchstander. 

What is underway? Not at anchor, not made fast to the shore, and 

not aground.

What is the limit for intoxication by alcohol? For recreational vessel 

operators the limit is .08 unless on waters within a State’s 

geographical boundaries if that State has established a blood alcohol 

level for purposes of finding “under the influence.” In that case, the 

State level applies. For instance, Michigan has a limit of .10 and so 

recreational vessel operators are not considered to be under the 

influence at .09 as they might in most other States. For commercial 

vessel personnel, the limit is .04. 

How can a BUI be determined? In the case of a recreational vessel 

operator, evidence that is sufficient to show that the person was in 

fact operating the vessel. In other words, documentation of the 

actual observation of the person operating the vessel to include some 

description of the person and his / her clothing, position held on the 
vessel (ie, master, passenger, crew, etc) and location of the person 

when observed “operating.” 

Additionally, acceptable evidence of intoxication is necessary. 

Acceptable evidence includes documented personal observations and 

/ or a chemical test. Observations of the person's manner, 

disposition, speech, movement, appearance, and behavior might be 

sufficient to conclude a person was under the influence. A chemical 

test (ie, breathalyzer) to determine alcohol content (discussed above) 

may be sufficient to conclude a person was under the influence. 

Often both observations and a chemical test are documented in a 

case file. Where no chemical test is directed, detailed documentation 

of the observations that led to a conclusion that the person was 

intoxicated is critical to support a violation. 

The administration of a chemical test first requires reasonable cause 

to believe that the operator is in violation of the stated limit 

(discussed above). Reasonable cause might be established by an 

articulation of those reasons that would motivate a person of 

ordinary intelligence under the circumstances to believe that the 

operator is suspected to be in violation of the standards. The Field 

Sobriety Tests (FSTs) are typically conducted as a reliable means to 

establish reasonable cause. Documentation, whether FSTs or 

statements, should “articulate” the basis for finding reasonable 

cause. The ultimate question is whether the tests, observations, etc 

provide a basis to suspect that the person is in violation of the 

standards articulated in 33 CFR 95.020 or 95.025. Only after finding 

reasonable cause can a chemical test be directed.

How is the chemical test administered? The operator is first 

informed that he or she is suspected of being in violation of the legal 

limit for boating under the influence and that he or she is being 

directed to undergo a chemical test. Documentation (ie, boarding 

officer statement) that reflects that the operator has been so advised 

and directed is always helpful. A chemical test is administered and 

the results are documented.

What is a refusal of a chemical test? A refusal by the party is an 

express or demonstrated determination not to submit to or cooperate 

in the administration of a chemical test. Such refusal is generally 
documented on the FSTs form. If not, it should be documented in a 

statement.

What does a refusal do? A refusal creates a presumption that the 

operator is under the influence of alcohol or a dangerous drug. The 

burden shifts to the person to overcome this presumption with 

evidence. 

A word about reasonable suspicion, reasonable cause and probable 

cause. From time to time we see boarding teams and parties alike 

get wrapped around the axle with these terms. Legal experts and 

pundits alike have tried to define these terms in varying degrees 

over the years. There are several “dictionaries” that define 

reasonable cause as probable cause and add that reasonable cause is 

more than reasonable suspicion which is more than mere suspicion. 

While a lively dissertation might be written here, it is not necessary 

to the topic. The only term used in the federal regulations, 33 CFR 

95, is reasonable cause. It is this that must be established to 

administer a chemical test.