DUI Evidence

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What Types of Evidence Are Considered in a DUI Case?

Drunk driving, or driving under the influence (DUI), is a criminal offense. The specific definition of DUI varies, but is usually akin to operating a motor vehicle while having a blood alcohol concentration of 0.08 or above. DUI laws may also penalize people who drive while impaired by any drug or alcohol, even prescription medicines. 

When a DUI case is heard in court, the judge or jury may consider various types of evidence that are related to the defendant’s level of intoxication while driving. Most evidence in a DUI case is gathered at the point of arrest and is called “field evidence.” In general, field evidence in a DUI case falls into five basic categories:

With field evidence, prosecutors analyze a variety of factors to determine whether to pursue a DUI case. Of course, one of the main items of evidence is the result of breathalyzer tests, blood, or urine samples from a field sobriety test. 

A person’s blood alcohol level at the time of arrest can sometimes lead to charges of “per se intoxication.” Per se intoxication means that the person is automatically deemed to be drunk driving if their blood alcohol content is above the legal limit. Thus, a driver may still be prosecuted regardless of how little their driving was affected.   

How Do Police Officers Determine Whether a Person Is Intoxicated?

In order to arrest a suspect for DUI, a police officer must first have reasonable suspicion to pull the car over and begin questioning the driver. If they suspect that the driver is drunk, they may attempt to conduct a field sobriety test which tests the driver’s motor skills. In some states, refusing these tests will result in an automatic suspension of the driver's license. In other states, such as California, it is entirely lawful to refuse to submit to such tests.

Intoxication is usually confirmed through the use of a hand held breathalyzer device. However, some states allow a police officer to conclude that a person is intoxicated based on their conduct or appearance. Some common symptoms of alcohol intoxication that police look for are:

If a police officer notes any of these symptoms, they will usually make a detailed report describing their observations. Depending on the evidence code of the state, this report may be used as evidence at a later time in court; however, it is most likely hearsay, and thus inadmissible. However, the officer may still testify as to their impressions and observations.

At times these symptoms can be even more incriminating than blood alcohol level readings. Alcohol affects every person differently; a person who has had only a small amount to drink already be physically impaired even if they are within the state limit for blood alcohol concentration.   

Do I Need a Lawyer?

DUI laws are an important part of maintaining highway safety. If you have concerns regarding the evidence used in your DUI case, you may wish to consult with a criminal defense lawyer for advice. Evidence is very technical in nature, and is best addressed through the expertise of an attorney.

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Last Modified: 09-03-2014 07:22 PM PDT

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