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Technically, there is no legal limit for DUI in SC, although you can be charged with “driving with an unlawful alcohol concentration” (DUAC) based solely on your blood alcohol content (BAC).

Below, we will discuss how blood alcohol content (BAC) works in SC and how it can affect your DUI case, including:

  • The “legal limit” for DUAC,
  • Why there is no “legal limit” for DUI,
  • How police determine what your blood alcohol content (BAC) is, and
  • How your BAC results can affect your DUI case.

What is the “Legal Limit” in SC?

When people say, “legal limit,” they are thinking that there is a certain blood alcohol content (BAC) above which a person is automatically guilty of driving under the influence.

This is true for DUAC charges – a BAC of .08 or greater is enough evidence to convict a person of DUAC, but not for driving under the influence charges, where the state must prove that a person was intoxicated to the extent that it materially and substantially affected their ability to drive, regardless of their BAC level.

What Does “Legal Limit” Even Mean?

“Legal limit” doesn’t refer to the number of drinks a person has had – there are far too many factors that affect how intoxicated a person becomes based on a set number of drinks, like whether the subject is male or female, their body size, how much they have had to eat, the amount of alcohol contained in a particular drink, the amount of drink in the container, and the person’s metabolism (the speed at which alcohol is processed through their system).

“Legal limit” usually refers to a person’s BAC – how much alcohol is contained in their blood at the time they were driving. Of course, there is a considerable amount of variability in how each person’s BAC affects their driving as well – male or female, body size, the amount of food eaten, the person’s metabolism, and the person’s tolerance level (regular drinkers must drink far more alcohol than casual drinkers to reach the same level of intoxication).


Below is a rough guideline as to what your legal limit may be, keep in mind that your own body chemistry may cause you to metabolize alcohol differently.

BAC for Women

Body Weight

(in lbs)

Number of drinksApproximate blood alcohol content (by percentage)
Beyond this point, your driving skills are likely affected, and you may face criminal penalties

BAC for Men

Body Weight (in lbs)100120140160180200220240
Number of drinksApproximate blood alcohol content (by percentage)
Beyond this point, your driving skills are likely affected, and you may face criminal penalties.


SC’s DUI law, found at SC Code § 56-5-2930, does not contain a “legal limit,” although certain inferences can be drawn based on the person’s blood alcohol content test results.

To get a conviction for DUI, the prosecution must prove that the person was:

  1. Driving,
  2. While under the influence of alcohol or drugs,
  3. “[T]o the extent that the person’s faculties to drive a motor vehicle are materially and appreciably impaired.”

Whether the person’s BAC was .07 or .20, they are not automatically guilty based on the BAC, although the BAC can be used as evidence against them. The State must prove, beyond any reasonable doubt, that the person’s faculties to drive were materially and appreciably impaired.


Driving with an unlawful alcohol concentration (DUAC) is different.

In contrast to DUI charges, to get a conviction for DUAC, the prosecution does not have to prove that the person’s faculties to drive were materially and appreciably impaired – they only need to prove that the person was 1) driving, 2) while their BAC was .08 or higher.

This means that a person who drinks regularly, who is larger than average size, who has a high metabolism of alcohol in their system, and who was not impaired can be convicted of DUAC based solely on their BAC result.

It also means that 1) if the BAC result is suppressed before trial, the prosecution will be unable to go forward with their case, or 2) the trial could become a “battle of the experts,” with each side’s experts testifying about why the machine was or was not reliable and what the actual BAC result should have been.

How do Police Determine Blood Alcohol Content (BAC)?

Three types of blood alcohol tests are used in SC – the Datamaster (breathalyzer), urinalysis, or blood analysis.

How the Datamaster (Breathalyzer) Machine Works

South Carolina uses the Datamaster DMT machine for breathalyzer tests – our police do not use PBTs (portable breath tests) on the roadside as police do in some other states. This means that people are usually arrested before they take the breathalyzer test, which is usually offered at the county jail before the person is booked.

How does the machine work? 

Before it tests your breath, the machine first conducts a simulation to test itself. If the test is successful, the machine continues to test your breath sample.

The officer will sometimes tell you to “blow, blow, blow harder,” because the machine is designed to test the “deep lung” air. It determines the alcohol content of the breath sample, but that is not the end of the analysis. The machine then multiplies its result by 2,100 to get a blood alcohol content result.

It is likely that many BAC results from breathalyzers are inaccurate based on the variation among individuals and many other issues that make these machines unreliable.

Blood or Urine Tests

Two other ways that SC police can get a blood alcohol content result to use against you at trial is through blood or urine tests.

Although it is not used as often as the breathalyzer or blood tests, urinalysis results are admissible at trial.

A urine or blood sample may be taken at a hospital by a trained nurse. Although in some states officers will draw blood themselves, in SC, officers will take a suspect to the hospital if they want a blood draw. In most cases, this is not done unless the suspect was involved in a motor vehicle accident and charged with felony DUI.

What the Results Mean for Your DUI Case

What do the BAC test results mean for your DUI case?

First, your license can be administratively suspended under SC’s implied consent laws if you refuse the test or if you take it and the result is .15 or greater.

Second, the results may be used as evidence against you at trial if your attorney is unable to get them suppressed.

SC Code § 56-5-2950 says that:

  • If the BAC test result is .05% or less, it is conclusively presumed that the person was not driving under the influence (although you can expect the officer to then claim that you were intoxicated on drugs and not alcohol),
  • If the BAC test result is higher than .05% but less than .08%, there is no inference either way, and
  • If the BAC test result is .08% or higher, there is a rebuttable inference that the person was under the influence.

A rebuttable inference means that you can cross-examine the officer or present evidence of your own to show that the machine’s result was incorrect.

For example:

  • Your Datamaster expert could testify as to how the machine operates and why it is likely or possible that the result was not accurate,
  • You can testify as to how you felt and whether your ability to drive was materially and appreciably impaired,
  • You can call “sobriety witnesses” to testify as to their observations of you before or during the driving,
  • You can show jurors your appearance on the roadside video, Datamaster room video, or officer’s bodycams, or
  • You can introduce any other evidence of 1) the machine’s failure or 2) your lack of impairment based on your attorney’s investigation of the case.

Questions About the Legal Limit in SC?

DUI lawyer Kent Collins will investigate your charges, answer your questions, and do everything legally and ethically possible to get your case dismissed, win your case at trial, or find a resolution that is fair and reasonable.

Get in touch with Kent by phone at 803-808-0905 or use this form to reach him online to schedule your in-person consultation.

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