For many people charged with DUI in South Carolina, the breath test result feels like the end of the case. It is not. A breath test is only as reliable as the machine, the operator, and the procedures used to obtain it, and South Carolina law gives drivers several ways to challenge the result. Our Charleston DUI defense lawyers regularly review breath test records, videos, and machine maintenance histories, and we have seen high readings excluded from evidence or used to negotiate better outcomes for our clients.
So can a DUI breath test be wrong in South Carolina? In this article, we explain what your breath test result means, the rules police must follow when administering the test, why a result can be wrong, and the legal tools available to challenge it.
Quick Answer: Yes. A DUI breath test in South Carolina can be wrong or inadmissible if the machine was not properly maintained, the operator did not follow the required procedures, the 20-minute waiting period was not observed, the required advisements were not given, or medical and physical factors affected the result. A reading of 0.08 percent or more only allows the jury to infer that a driver was under the influence; it does not mean the driver is automatically guilty.
Table of Contents
- What Breath Test Machine Is Used in South Carolina?
- What Does Your Breath Test Result Mean?
- Does a High Breath Test Reading Mean You Are Guilty of DUI?
- How Does Your Breath Test Result Affect Penalties and Your License?
- What Rules Must Police Follow When Giving a Breath Test?
- Why Can a DUI Breath Test Result Be Wrong?
- Can an Officer Tell You to Blow Hard Into the Breath Test Machine?
- What Is a Landon Motion in a South Carolina DUI Case?
- Do You Have the Right to an Independent Test?
- What Happens If You Refuse the Breath Test?
- How Can a Charleston DUI Lawyer Help?
What Breath Test Machine Is Used in South Carolina?
South Carolina’s breath testing program is run by the State Law Enforcement Division (SLED), which approves the devices that may be used and sets the procedures for using them. SLED lists the approved devices in its policy and procedures manual under S.C. Code Regulation 73-2. For many years, the DataMaster DMT has been the breath testing instrument used in South Carolina DUI cases, and recent South Carolina proceedings continue to describe DataMaster tests. The DataMaster measures alcohol in a person’s deep lung air and converts that measurement into an alcohol concentration.
Because the machine is a complex electronic instrument, its result depends on proper calibration, maintenance, and operation. That is why the records and video associated with each test are so important in a DUI defense.
What Does Your Breath Test Result Mean?
Under S.C. Code Section 56-5-2950(G), the law gives different effects to breath test results depending on the alcohol concentration at the time of the test:
| Alcohol Concentration at the Time of the Test | What the Law Provides |
|---|---|
| 0.05 percent or less | It is conclusively presumed that the person was not under the influence of alcohol. |
| More than 0.05 but less than 0.08 percent | No inference can be drawn either way, but the result may be considered with other evidence. |
| 0.08 percent or more | It may be inferred that the person was under the influence of alcohol. |
A result of 0.05 percent or less does not prevent the State from trying to prove that a driver was impaired by drugs or another substance. A result of 0.08 percent or more may also support a charge of Driving With an Unlawful Alcohol Concentration (DUAC) instead of DUI if the State can prove the statutory requirements, including that the driver’s alcohol concentration was at least 0.08 percent while driving; a person may not be prosecuted for both offenses for the same incident.
Does a High Breath Test Reading Mean You Are Guilty of DUI?
No. A reading of 0.08 percent or more creates a permissible inference, not a conclusive presumption, in a DUI case. At trial, the jury may be told it may infer the driver was under the influence, but it must consider that inference with all other evidence, including the driving, the field sobriety tests, and the video of the arrest. The jury is not required to find the driver guilty based on the number alone.
When our client has a significant reading, we look for ways to challenge it. If the case goes to trial, we try to keep the reading out of evidence so the jury never hears it. Before trial, we use the weaknesses in the breath test to negotiate with the prosecutor. In one case our firm handled, a client registered 0.17 percent on the DataMaster, but the video of the field sobriety tests showed no signs of intoxication.
Before trial, our attorney Tom Nelson presented the prosecutor with two arguments for excluding the result. First, the officer told our client twice to “blow as long and as hard as he can,” even though the DataMaster owner’s manual instructs operators not to tell a subject to blow hard.
An expert retained by our firm, a former officer with years of training on the machine, was prepared to testify that the instruction violated proper operating procedure, that our client exhaled about 2.3 liters of air when the machine requires about 1.5 liters, and that the breath profile showed a significant spike. Second, the officer had not given our client the required written copy of his rights. The prosecutor offered a plea to a lesser charge in exchange for dismissing the DUI, and our client accepted. Every case is different, but this example shows how to challenge a breath test.
How Does Your Breath Test Result Affect Penalties and Your License?
Your breath test result can also affect the penalties you face and whether your driver’s license is suspended before your case is ever decided. The following table summarizes the key thresholds:
| Breath Test Result | Effect |
|---|---|
| 0.08 to less than 0.10 percent | Base penalty level for DUI and DUAC; a first offense carries a $400 fine or 48 hours to 30 days in jail. |
| 0.10 to less than 0.16 percent | Increased penalties; a first offense carries a $500 fine or 72 hours to 30 days in jail. |
| 0.15 percent or more | Administrative license suspension under Section 56-5-2951: one month for a first occurrence, and two, three, or four months for later occurrences within ten years. |
| 0.16 percent or more | Highest penalty level; a first offense carries a $1,000 fine or 30 to 90 days in jail. |
Penalties for second and later offenses increase at each level. After a 0.15 suspension, you have 30 days from issuance of the notice of suspension to request a contested case hearing, and under changes that took effect on May 19, 2024, you may be able to enroll in the ignition interlock program to end the remaining suspension, subject to an ignition interlock restricted license and a minimum device period of three months. For more details, see our articles on DUI penalties in South Carolina and DUI license suspensions in South Carolina.
What Rules Must Police Follow When Giving a Breath Test?
South Carolina law and SLED’s regulations set specific requirements for breath testing. The following table summarizes the most important ones:
| Requirement | What the Law Requires |
|---|---|
| Timing | The breath sample must be collected within two hours of the arrest (Section 56-5-2950(A)). |
| Qualified operator | The test must be administered by a person trained and certified by the South Carolina Criminal Justice Academy under SLED’s policies. |
| Advisements | After the video is turned on and before the test, the person must receive a written copy of, and be verbally told, their rights, including the right to refuse, the consequences of refusing or of a result of 0.15 percent or more, the right to an independent test, the 30-day deadline to request a hearing, and the requirement to enroll in an Alcohol and Drug Safety Action Program if no hearing is requested or the suspension is upheld (Section 56-5-2950(B)). |
| Waiting period | The person’s conduct during the 20-minute waiting period before the test must be video recorded, unless the officer submits a sworn affidavit certifying that recording was physically impossible (Section 56-5-2953). |
| Simulator check | Before the subject’s test, a 0.08 percent simulator test must read between 0.076 and 0.084 percent. |
| Device inspections | SLED must inspect each certified device after repairs and ensure a SLED inspection was performed within the three months before a subject test; SLED must keep certification and inspection records for at least five years (Regulation 73-2). |
| Maintenance records | SLED and each agency with a breath testing site must keep detailed electronic records of malfunctions, repairs, complaints, and other problems; the records, including remarks, must be entered into a breath testing device and made available on SLED’s website (Section 56-5-2954). |
Not every mistake leads to exclusion. Under Section 56-5-2950(J), a failure to follow the statute or SLED’s procedures requires exclusion of the result when the judge or hearing officer finds that the failure materially affected the test’s accuracy or reliability, or the fairness of the testing procedure. That is why a careful review of the video and the records matters. For more on the video requirement, see our article on whether police have to video record a DUI arrest in South Carolina.
Why Can a DUI Breath Test Result Be Wrong?
A breath test does not measure the alcohol in your blood directly. It measures alcohol in your breath and reports an alcohol concentration based on that sample. Defense experts have identified a number of factors that may cause a breath test result to be higher than a person’s true alcohol concentration, or that may make the result unreliable:
- Mouth alcohol and acid reflux: the machine is designed to test air from the deep lungs. Alcohol in the mouth or throat, including alcohol brought up by acid reflux (GERD), can cause a falsely high reading. This is one reason the waiting period and observation before the test matter.
- Breathing pattern: the alcohol concentration in a person’s breath can change as they exhale, so an irregular or interrupted sample may raise questions about the result.
- Body temperature: a fever or other temperature-related condition may affect a breath reading in some circumstances.
- Individual physiology: the relationship between breath and blood alcohol varies from person to person, although South Carolina’s breath-testing law uses the reported alcohol concentration rather than requiring a direct blood-alcohol measurement.
- Medical conditions: conditions such as diabetes and hypoglycemia can produce symptoms that look like impairment, and in some circumstances breath chemistry may warrant further examination.
- Radio frequency interference: electronic interference from radios or phones near the machine may affect the instrument if its safeguards do not prevent it.
- Simulator solution problems: if the simulator solution used to check the machine was not properly prepared, the check may not confirm the machine’s accuracy.
- Improper maintenance: missing repair records, overdue inspections, or problems reported close in time to the test can call the result into question.
- Operator error: failing to observe the waiting period, failing to give the required advisements, or giving improper instructions can affect the result or its admissibility.
Whether any of these factors apply depends on the facts of the case, and some require expert testimony. Over the years, our lawyers have cross-examined the officials responsible for maintaining breath test machines and found missing repair records and procedures that were not followed.
Can an Officer Tell You to Blow Hard Into the Breath Test Machine?
Officers sometimes tell people to “blow hard” into the breath test machine. According to the DataMaster owner’s manual, the best breath sample comes from a continuous exhalation and does not need to be a hard blow. The manual also warns operators not to tell the subject to blow hard. The machine is designed to read a smooth, steady exhalation, and an instruction to blow hard, or an unusually long blow, may provide grounds to examine whether the sample was reliable.
Because the breath test procedure must be video recorded, the video often shows exactly what the officer said. If you were told to blow hard, that instruction may support a challenge to the result’s reliability, as it did in the case described above. We have defended many cases in which the person did not appear impaired on the video, but the machine still produced a reading above the legal limit.
What Is a Landon Motion in a South Carolina DUI Case?
A Landon motion challenges the reliability of the breath test machine based on its maintenance and repair records. It is named after State v. Landon, 370 S.C. 103, 634 S.E.2d 660 (2006). In that case, the South Carolina Supreme Court held that the abbreviated records SLED then kept did not satisfy the requirement in Section 56-5-2954 for a detailed record of machine malfunctions, repairs, and complaints. The Court also held that deficient records do not automatically require suppression of the result.
Instead, because the machine information is controlled by the State, a defendant who makes a prima facie showing of prejudice, such as evidence of a repair close in time to the test, shifts the burden to the State to show that the defendant was not prejudiced. In Landon, a repair eight days after the test was enough to make that showing, and the case was sent back for a hearing on prejudice.
Later cases show how these challenges play out. In Murphy v. State, 392 S.C. 626, 709 S.E.2d 685 (Ct. App. 2011), a repair 16 days after the test did not make the result inadmissible, because evidence of at least 25 successful self-checks between the test and the repair supported a finding that the machine was working properly.
The Supreme Court’s earlier decision in State v. Parker, 271 S.C. 159, 245 S.E.2d 904 (1978), also recognized that the State may be required to show that the machine was working properly, the correct chemicals were used, the person had nothing in their mouth during the waiting period, and a qualified operator administered the test properly. Knowing which records to request, how to interpret them, and how to present a Landon motion is an important part of defending a DUI case.
Do You Have the Right to an Independent Test?
Yes. Under Section 56-5-2950, a person who takes the breath test may have a qualified person of their choosing conduct additional tests at their own expense, and the person must be told about this right in writing. If the person asks, the arresting officer must provide affirmative assistance in contacting a qualified person to conduct the test, which at a minimum includes transportation to the nearest medical facility that performs blood alcohol testing. If the officer fails to provide the required assistance after a request, the breath test result is not admissible in a court or administrative proceeding.
Whether the officer met this duty depends on the circumstances, including whether the person actually made a request. South Carolina courts have addressed these issues in cases such as State v. Knighton, 334 S.C. 125, 512 S.E.2d 117 (Ct. App. 1999), and State v. Brown, 436 S.C. 505, 873 S.E.2d 445 (Ct. App. 2022).
What Happens If You Refuse the Breath Test?
You have the right to refuse the breath test, but refusing results in an administrative suspension of your driver’s license, and the refusal may be used as evidence at trial. You have 30 days from issuance of the notice of suspension to request a contested case hearing to challenge the suspension, and you may have options to keep driving while the case is pending.
For a complete explanation, see our article on what happens if you refuse a breath test in South Carolina. You can also learn more about the tests officers give before an arrest in our article on field sobriety tests in South Carolina.
How Can a Charleston DUI Lawyer Help?
A breath test result can affect whether you are convicted, the penalties you face, and whether you keep your license. The attorneys at Futeral & Nelson have defended DUI cases in Charleston, Berkeley, and Dorchester Counties since 2003. We obtain the breath test records, the machine’s maintenance history, and the test video, and we look for every procedural and scientific issue that may make the result unreliable or inadmissible. For more information about DUI defense, you can also download our free book on DUI in South Carolina.
If you have been charged with DUI in Charleston or anywhere in the Lowcountry, call us at 843-284-5500 or contact our Charleston DUI defense lawyers at Futeral & Nelson, LLC today to discuss your case.
