How is BAC Calculated?

By Jonathan Blecher on May 29, 2024

If you have been arrested for a DUI in Florida, your future is at stake. Jail time, heavy fines, and other consequences are possible. But with a Miami DUI Defense attorney at your side, the odds of obtaining a favorable case outcome rise dramatically. One of the critical pieces of evidence the police have is your blood alcohol content (BAC) test results. A better case resolution is possible if this crucial evidence is challenged.

Jonathan Blecher Criminal Defense has defended thousands of clients in his 40-year legal career. Many DUI cases have resulted in acquittals, dismissals, and reduced charges, and Attorney Blecher will fight for the best case outcome for you. Attorney Blecher enjoys a 10.0 Superb Avvo rating and is on The National Trial Lawyers: Top 100 list.

What Is Blood Alcohol Content (BAC)?

A cornerstone of many drunk driving cases is blood alcohol content or BAC. BAC means the percent of alcohol (ethanol or ethyl alcohol) in your bloodstream. If your BAC measures .10%, it means that your blood results contain one part of alcohol for every 1,000 parts of blood. In other words, there were .10 grams of alcohol per 100 grams of your blood. BAC tests are used in Florida and other states to measure if a person is under the influence of alcohol.

In Florida, blood alcohol content is typically measured after a traffic stop with a breath, blood, or urine test. Blood testing can be difficult because many people are afraid of needles or could have infectious diseases. For a blood test, the police must take you to a clinic or hospital and have a medical professional draw your blood. This process means more time passes between the arrest and test.

Breath testing in the field after the arrest is the most common because it is the most straightforward test to administer. But skilled criminal defense attorneys question breath test results all the time. Urine tests are considered less accurate than blood tests and are used less often.

Florida has an implied consent law. This means that the police can compel you to take a blood or breath test if they suspect you are under the influence. If you refuse, your driver’s license will be suspended, and the refusal may also be used against you in court.

BAC Legal Limits In Florida

Your BAC level is essential in Florida because the state has a legal limit. If your BAC is .08% or higher in most cases, it is considered DUI per se, meaning you are too drunk to drive legally. You also can be charged with a Florida DUI even if your BAC is not .08% or higher. If you are under 21, the legal limit in Florida is .02%.

However, it is more challenging for the prosecutor to convict you if your BAC is under the legal limit. The state prosecutor must possess independent evidence that you were impaired, such as your behavior or field sobriety test (FST) results.

If you are convicted of drunk driving for the first time in Florida, you could be sent to jail, but there is no minimum jail time. You will be fined at least $500 and your license can be suspended for up to six months.

BAC Test Variables

Your BAC will differ primarily based on your weight and how your body responds and metabolizes alcohol. The length of time you drank, the time since your last drink, your body weight, and more can influence your BAC.

For instance, if you are a 120-pound woman and have three glasses of wine in 60 minutes, your BAC will be approximately .09%, which is over the limit in Florida. But if you are a 200-pound man with the same amount of wine, your BAC could be as low as .04%.

Regardless of how much you have to drink to reach a given BAC, once you reach it, you will exhibit signs of intoxication. For example:

.10 to .029%: Most people will act normally.
.020 to .059%: Most people will act relaxed, happy, and talkative. You could have trouble concentrating on a task.
.06 to .09%: Most people will have lowered inhibitions and act more extroverted than usual. You could struggle with reasoning, peripheral vision, and depth perception.
.10 to .19%: Most people will express themselves more strongly than usual and may have severe mood swings. They could have slower reaction times and reflexes, including staggering and slurred speech.

BAC Myths And Misconceptions

The following myths and misconceptions are common regarding BAC and DUI in Florida:

The Breath Test Is Optional

According to Florida’s implied consent laws, you are required to submit to a breath, blood, or urine test. Your license can be suspended if you refuse to take a breath test. However, the Florida Supreme Court has said that if a DUI arrest is illegal, your license cannot be suspended for refusing the test. Attorney Blecher will review the circumstances of the arrest to ensure it was conducted legally.

Also, a breath test can be administered by the police without a warrant. It’s minimally invasive, so this holds up in court. But the police do need a warrant to test your blood in most situations.

Breath Tests Are As Accurate As Blood Tests

Blood tests are the most accurate, but breath tests are more common because they can be administered in the field. A breathalyzer’s test result can be close to blood test results, but it is only an estimate based on the alcohol vapor it detects on your breath.

Breath Test Results Are Infallible

Breath tests are only sometimes accurate. For example, if the machine is improperly calibrated, the result could be off by up to .02%. Many DUI charges have been dismissed because of inaccurate or unreliable breathalyzer test results.

You Can Lower Your BAC With Food Or Drink

There are many online myths about how to reduce your BAC, such as by eating a particular food or combining alcohol with energy drinks. These aren’t true. The only way to reduce your blood alcohol content is for time to pass. Your BAC will decrease by about .015% per hour for every hour you don’t drink. If your BAC is .10% – legally intoxicated in Florida – it will take more than six hours for you to become legally sober.

You Have To Be Driving To Be Charged With DUI

If you are in physical control of a vehicle, you can be charged with a Florida DUI. For example, if you are intoxicated and sitting in the driver’s seat with the keys, it doesn’t matter if you aren’t driving. For all intents and purposes, in Florida, you are drinking and driving.

How A Miami DUI Attorney Can Challenge BAC Evidence

Being declared legally intoxicated in Florida after an arrest is scary, but BAC test results are critical to proving the case against you. Many DUI defense attorneys successfully challenge BAC results. Attorney Blecher can review the facts of your case and devise the best strategy to question the evidence against you. Some common approaches to challenge BAC results are:

Breathalyzer test problems: Breath test devices must be tested and calibrated regularly for accuracy. Failure to do so may trigger an inaccurate reading. Furthermore, various external factors can cause false positives, such as certain diets and breath alcohol from mouthwash. If the police didn’t observe you for 20 minutes before giving the test, your attorney can challenge the evidence.
Blood test mistakes: Blood tests are generally considered accurate but they can have problems. A trained medical professional must administer the test. The blood could be improperly drawn or stored incorrectly, possibly contaminating or fermenting the sample.
Field sobriety test errors: Before the police administer the BAC test, they may perform field sobriety tests on you. Several tests are standard but they aren’t infallible. Many things, such as poor weather, uneven surfaces, uncomfortable footwear, and more, can influence FST results. If your lawyer can prove the FSTs were given in suboptimal conditions, probable cause may be weakened.
Improper stop: Your lawyer can also challenge the legality of the traffic stop. The BAC test results may be inadmissible in court if there was no probable cause to stop you.

Successfully challenging BAC evidence is difficult and requires understanding the law, science, and facts of your DUI case. A skilled DUI attorney can review your case and identify potential areas to challenge. Then, they will devise a defense to mitigate the impact of the DUI charge.

Contact Miami DUI Attorney Jonathan Blecher For Your DUI Defense

If you face a DUI charge in Miami, don’t deal with the aggressive, well-funded state prosecutor on your own. The state of Florida will devote ample resources to convicting you. However, a skilled DUI attorney can make all the difference.
Jonathan Blecher Criminal Defense Attorney has defended thousands of people successfully against DUI and other serious charges. Many of his clients have had their cases dropped, and he will fight for the best outcome in your situation. Contact Attorney Blecher today at (786) 745-7856 for a DUI case consultation.