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How Does a Blood Draw Work for a DUI?

Sabah Khalaf
10 minute read

Did you know that when you get pulled over for driving under the influence (DUI), a breathalyzer isn’t the only test you could receive? Most people are familiar with the breathalyzer, but don’t know about the possibility they could be given a blood test instead. Let’s dive into how a blood draw works, how it’s different from a breathalyzer, and what you should do next if you’ve taken one.

What is the State’s test?

If you’re pulled over for DUI in Oklahoma, the officer will offer you an opportunity to take the State’s test. This is a test designed to determine your blood alcohol content (BAC), and is either a breathalyzer test or a blood test. You’ll typically be given a breathalyzer, but you might be given a blood test in certain situations. The results of the test help the State determine whether you were under the influence at the time of your arrest.

What is the legal limit for alcohol?

The legal limit for alcohol is a .08 BAC. However, you can be charged with driving while impaired (DWI) if your BAC is a .06 or higher. If you have a BAC of .15 or higher, you can be charged with an aggravated DUI.

What is the legal limit for marijuana?

There isn’t a legal limit for marijuana. Any amount of THC in your system is an illegal amount for purposes of a DUI. The same can be said for all other controlled substances. Any amount of an illegal substance, such as heroin or methamphetamine, is an illegal amount for the purposes of driving.

This is important to emphasize: You can legally use marijuana in the State of Oklahoma, but if it is in your system while driving, you will receive a DUI-Drugs. This is true even if you are no longer experiencing the effects of marijuana.

What is a breathalyzer?

A breathalyzer is a machine you blow into that measures your BAC and displays it on the device as a number. During the test, you’ll blow into the device, and your breath will travel through a chamber containing chemicals that react with alcohol. The strength of the reaction is used to calculate the BAC that appears on the screen.

Does marijuana show up with a breathalyzer?

No, breathalyzers will not show marijuana in your system. Breathalyzers are designed to measure alcohol only. While law enforcement is in the process of developing a breathalyzer that will detect marijuana in a person’s system, it has not yet been approved for use as evidence in a criminal court.

What is a DUI blood draw?

A DUI blood draw is taken at a hospital by a nurse. They must follow a specific procedure to draw the blood, store it, and ship it to an approved laboratory for testing. This can sometimes take a few months, but it provides much more information than a breathalyzer.

A blood draw not only provides your BAC, but also provides information about all other substances within your system. This includes illegal controlled substances, such as methamphetamines and heroin, as well as legally obtained substances, such as marijuana or pain medication. The results of your blood draw can affect whether or not you receive criminal charges. For example, if a blood draw shows that your BAC is a .05, which is under the legal limit, but your system also contains marijuana, you will still be charged with a DUI-Drugs.

Breathalyzer vs. blood test: Main differences

The biggest difference between a breathalyzer and a blood test is that a breathalyzer provides immediate results, while it can take one to three months or more to get blood test results. However, if the officer’s breathalyzer is broken, if they suspect you of driving under the influence of drugs instead of alcohol, or if there are other factors that might prevent an accurate breathalyzer reading, they’ll give you a blood test.

Another big difference is that the officer will have to take you to a hospital for a blood draw. According to the Oklahoma Board of Tests, only certain licensed people, like doctors and nurses, can draw blood for the test. There are also many other requirements for blood tests, like using only certified laboratories and recording the chain of custody for the sample. If the officer doesn’t follow the rules, that could be one way to get your case dismissed.

Do I have a choice in which test I can take?

No, you don’t. The arresting officer will ask your permission to take the State’s test, but they will not give you a choice between a breathalyzer or blood test. The officer will make that decision themselves. An officer will ask if you would like to take the State’s test, and once you say yes, they will either administer the breathalyzer or take you to a hospital for a blood draw.

While you generally can't choose which test to take, if you take a blood test as your State’s test, you also have the right to have that sample tested at an independent lab. Your attorney can help you navigate the process.

Can I refuse to take the test?

Yes, you can refuse both a breathalyzer and a blood test. You can also say you no longer wish to take the test at any point. For example, if you said yes because you expected to take a breathalyzer test, and an officer takes you to a hospital for a blood draw, you can say you no longer wish to take the State’s test. While this can be used against you in trial, an officer can’t force you to take the test.

What happens if I refuse to take the test?

Just because you refuse to take the State’s test doesn’t mean you won’t be charged. A refusal of the State’s test can be admitted as evidence and can be used to show that you were most likely intoxicated at the time. However, the State has the burden of proof, which means they must prove that you were intoxicated. It is not up to you to prove that you weren’t intoxicated.

No, an officer can’t take your blood for testing without your consent. While this may initially seem like an outlandish scenario, it’s more common than you might expect. Many people end up unconscious after DUI accidents or pass out in their vehicles due to intoxication. If an officer finds you unconscious, they cannot take you to a hospital and draw your blood without your consent. This is true even if your blood must be drawn for medical treatment: The officer can’t take a sample of the blood for testing.

The case that established the rules

The case that established this rule is called Stewart v. State. In the case, the defendant was driving while under the influence. He stopped his vehicle in the middle of the lane, causing an accident that led to the serious injury of three people and death of two others.

The defendant was transported to the hospital, alongside the other victims, for treatment of his injuries. During treatment, a state trooper instructed a registered nurse to draw the defendant’s blood and submit it for testing. This occurred while the defendant was unconscious and the trooper did not have the defendant’s permission, nor did he have a search warrant.

The blood test results confirmed that the defendant had methamphetamine and marijuana in his system. The defendant argued the blood draw was a violation of his constitutional rights, specifically his protection against unreasonable searches and seizures. While most people know this right applies to searches of your home or vehicle, it also applies to searches of your person.

The court agreed with the defendant’s argument, and found that this right also applies to the blood inside your body. Therefore, the trooper needed either a search warrant or the defendant’s permission to test the defendant’s blood.

Can an officer get a search warrant for my blood?

Yes, an officer can get a search warrant to draw your blood, but it’s rare. There is a specific legal process for getting a search warrant, and it must be approved by a judge. This can take a while, which is why officers usually just ask for your consent to draw blood. Typically, judge’s don’t grant search warrants for basic DUIs. They normally only grant a search warrant when a person is killed or very seriously injured. Regardless, search warrants are rarely obtained while the evidence is fresh enough to be admitted at trial.

The bottom line

If you’ve been given a blood test as part of your DUI arrest, it’s important to contact an experienced attorney as soon as possible. It’s also important to remember that a positive blood test doesn’t mean the end of your case. Your attorney can help you not only navigate getting your test results and sending a sample for independent testing, but also help you build a defense, get a plea deal, or even get your case dismissed. Contact the Tulsa DUI Guy today to see how we can help you get the best outcome for your case.