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Direct And Circumstantial Evidence In DUI Cases

Now that the United States Supreme Court has legalized refusal-to-submit laws, at least to some extent, more DUI prosecutions will probably be based on direct evidence of intoxication. Blood draws are the most accurate way to measure a person’s blood alcohol content (BAC), but peace officers must obtain search warrants prior to blood draws, and except for the occasional “no refusal weekend” or other high-enforcement period, most law enforcement agencies do not take this extra step.

Direct Evidence

The Breathalyzer in use today is essentially the same one that was in use in the 1980s, and as the name implies, it measure the amount of alcohol in a person’s breath, not the amount in a person’s blood. Essentially, a computer estimates the BAC based on the amount of breath alcohol. No technology is perfect, and the Breathalyzer certainly isn’t perfect. There are a number of flaws that come into play, and they are especially relevant in borderline BAC cases, like a .08 or .09:

  • Absorption: If the suspect has consumed any alcohol in the last half-hour or hour, it is still being absorbed into the blood and the person’s BAC is actually a little lower than the test results indicate.
  • Acetone: Diabetics, dieters, and some smokers all have elevated acetone levels, which shows up as alcohol in Breathalyzer tests.
  • Mouth Alcohol: Suspects must be continually monitored for at least fifteen minutes prior to a Breathalyzer that to ensure that they do not belch or vomit, because these actions, and others like them, increase the amount of mouth alcohol and skew the test results.

Attorneys often partner with expert witnesses to explain these flaws to the juries and help them make informed decisions.

Circumstantial Evidence

Statistics vary by jurisdiction, but about one suspect in five refuses to submit to a breath test. Although officers could force them to submit to blood tests, they normally rely on exercises. Like all circumstantial evidence, the three approved exercises can all be challenged in court:

  • Horizontal Gaze Nystagmus: The HGN test, in which subjects follow fixed points with their eyes without moving their heads, is about 85 percent accurate when predicting intoxication, but a number of conditions and substances other than alcohol cause involuntary eye movements that may be misjudged as nystagmus.
  • Walk And Turn (WAT): The heel-to-toe walk test basically measures agility. Officers are supposed to have suspects walk an actual line as opposed to an imaginary line, but that is not always the case.
  • One Leg Stand (OLS): This agility test has some of the same shortcomings as the WAT.

The WAT and OLS both measure mental ability as well, because they require the suspect to follow directions.

In court, officers always tell the jury that the driver “failed” the tests, and they often base their assessment on hyper-technical flaws, like starting the WAT with the wrong foot or taking an incorrect number of steps. But the jury gets the final say as to whether or not the defendant was intoxicated, and there is a difference between intoxication and nervousness or misunderstanding.

Rely on Experienced Attorneys

Both direct and circumstantial evidence in DUI cases can be successfully challenged in court. For prompt assistance in this area, contact an experienced criminal defense attorney in Port St. Lucie. At Eighmie Law Firm, P.A., after hours visits are available.

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