DUI: The Legal Limit Myth


The expression that an individual charged with Driving Under the Influence (DUI) was over the limit as regards the person’s blood alcohol content (BAC) perpetuates yet another DUI myth. First, let me explain what is being expressed. Most often, as there are exceptions, an individual arrested for DUI will be offered the opportunity to submit a breath sample to determine BAC. It is a common myth that a person who chooses to submit a breath sample (and yes it is a choice) and registers a BAC of .08 (eight one hundreths of one percent) or greater is over the legal limit.

First, the news flash is that there is no such thing as a legal limit. Mention of a legal limit in this context implies that an individual has crossed a threshold that dooms them to a DUI conviction, together with the penalties and the many negative consequences of a DUI conviction. This myth stems from a misunderstanding of DUI law, as well as the fact that law enforcement often uses the term legal limit as well.

The misunderstanding is a result of the following. Pursuant to South Carolina law, a BAC of .08 or greater creates a permissible inference that an individual is under the influence, or impaired by alcohol as that term is defined. However, simply stated, what this means is that if the case were to go to trial and then to the jury to deliberate the case, the law explained to the jury prior to deliberation would include a statement, and its wording can vary, but basically explaining that if one has registered a .08 or greater, the jury may infer that the individual was under the influence. The judge’s statements to a jury of the relevant law in a case are commonly referred to as the Judge’s charge to the jury. The Judge will advise and explain the relevant law to the jury following the presentation of all evidence in the case and prior to the jury’s deliberation.

The important point is that the evidence of a BAC of .08 or greater only creates a permissible inference of guilt, meaning that if a jury chooses to do so, it may base a finding of guilt on this evidence alone. However, under no circumstance is a jury told to disregard all other evidence presented in the case. Such other evidence could include the reliability of the breath testing device, the appearance and conduct of the defendant on video, and any other evidence in the case. A jury that finds the alleged BAC of .08 or greater to be true beyond a reasonable doubt is not required to find the individual guilty.

I have tried many DUI cases with a jury in cases alleging a BAC of .08 and many different levels well above .08 resulting in a verdict of not guilty. I have also handled many of these cases resulting in dismissal without a trial as well.

However, it should be noted that a separate offense titled Driving With an Unlawful Alcohol Content (DUAC) is a law intended to require guilt based upon two elements: (1) driving a motor vehicle, and (2) a BAC of .08 or greater. However, this offense is not often charged by law enforcement, for reasons not the subject of this article. However, it should also be noted that even in a case of DUAC, the law charged to the jury is to consider all of the evidence in the case when determining the reliability of the breath testing device. Therefore, the defense of a DUAC is generally not much different than the defense of a DUI, although in the former, the use of an expert witness who can expertly address the breath-testing device is more common. Although, it is often advisable to use an expert witness in a case of DUI where there is evidence of a BAC of .08 or greater as well.

Last, it should not be overlooked that any DUI trial with a BAC of .08 or greater should include a vigorous defense as to what, if any, weight to give to a BAC of .08 or any level. Some years back, the permissible inference of DUI was lowered from .10 to .08. In other words, the state legislature voted to make the change. So, a jury is permitted to infer guilt based upon a .08 BAC as a result of politicians selecting .08 as the magic number. Why not .07 or .09? Exactly! Any competent DUI defense should point out the arbitrary nature of the law. Impairment by alcohol may be based upon a BAC of .08 or greater simply as a result of a vote in the legislature, hardly scientific. In this author’s opinion, due process and justice requires that a jury never base its vote of guilt solely on the BAC of an individual, but rather base its vote on the evidence presented in addition to the alleged BAC. Otherwise, the jury is simply finding guilt as a result of what number the legislature believed should equal impairment.

In any event, rest assured, there is no legal limit.