If you are stopped for suspected drunk driving, one of the first things police may ask you to do is take a breath test. This test helps them measure how much alcohol is in your body at the time of the stop. Many people have heard of breathalyzers, but few know how they actually work or what the results mean.
Frances Prizzia Criminal Defense Lawyers helps people understand their rights when it comes to alcohol breath tests. We also know that breath test results are not always perfect. There are many things that can affect the outcome. That’s why we fight for clients who may have been wrongly accused or tested unfairly.
A breathalyzer test is a tool used by police to find out how much alcohol is in your breath. When you blow into the device, it measures the alcohol concentration in your breath and gives an estimate of your blood alcohol content (BAC).
This estimate is not a direct measure of your blood. Instead, it uses a formula to guess how much blood alcohol is in your system based on the air from your lungs. Police use this result to decide if you are over the legal limit for driving.
A breath test is quick, but it can have problems. The results depend on the machine, how it’s used, and what’s going on in your body. Even things like breath fresheners, health problems, or how recently you were consuming alcohol can affect the test.
Still, law enforcement officers often treat the number as fact. That’s why you must understand how these tests work and what they really mean.
Police use breath alcohol tests during DUI traffic stops when they think a driver may be drunk or under the influence of alcohol. They may notice signs like swerving, slurred speech, or the smell of drinking alcohol. If they suspect alcohol impairment, they may ask for a breath sample.
In California, drivers are often first given a preliminary alcohol screening (PAS) test. This is a handheld device used during the stop. If the driver is arrested, a second test may follow at the station using a larger, more accurate machine.
The breath alcohol test gives the officer a fast way to check your blood alcohol level. If the result shows a BAC at or above 0.08%, which is the legal limit for most drivers, it can lead to an arrest and DUI charge.
However, these tests are not perfect. False readings can happen, and outside factors can affect the results. That’s why legal help is essential.
When you drink, alcohol doesn’t stay in your stomach. It travels through your body and ends up in your breath. This is why alcohol in your breath can be measured with a breath sample.
When you start drinking alcohol, it passes through your mouth, throat, and into your stomach. From there, alcohol moves quickly into your small intestine, where it is absorbed into your blood. This process begins just minutes after consuming alcohol and can continue for about 30 to 90 minutes, depending on how much you drink and whether you’ve eaten food.
Once the alcohol is in your blood, it travels all over your body. This includes your brain, which is why alcohol impairment happens — your brain and thinking are affected. It also travels to your lungs, and that’s where blood alcohol concentration starts to show up in your breath.
This is why a breath sample can be used to estimate your blood alcohol content. The more you drink, the higher the alcohol concentration in your breath.
As alcohol present in the blood reaches the lungs, some of it moves into the air sacs deep in the lungs. These sacs are where your blood and breath meet. When you breathe out, a small part of the alcohol concentration from your blood passes into your breath.
The alcohol leaves your body as part of the air you exhale. This is called alveolar air, which comes from deep inside your lungs. That’s why law enforcement officers want a deep, strong breath when you give a breath sample. They are looking for this deep lung air, not just the air from your mouth.
The more alcohol you've consumed, the more alcohol your lungs will release into your breath. That’s how the breath alcohol test can estimate your blood alcohol content without needing a blood sample.
To estimate your blood alcohol level from a breath sample, machines use a set formula. In California, the most common rule is that 2,100 milliliters of breath is equal to 1 milliliter of blood in terms of alcohol concentration. This is called the breath-to-blood ratio.
The number comes from research, but not everyone’s body follows it exactly. Some people absorb or release alcohol at different rates. This means your actual blood alcohol content (BAC) might be higher or lower than the number shown on the machine.
Still, the law treats the result as strong proof. If your breath shows a BAC of 0.08% or more, that’s over the legal limit for most drivers in California. But this ratio is only an estimate. That’s why Frances Prizzia Criminal Defense Lawyers looks closely at the test method and machine accuracy in every case.
There are two main types of machines used for alcohol breath tests. Here are the types of breathalyzer test devices:
The first type is called a Preliminary Breath Test or PBT. Police often carry these small, handheld machines in their patrol cars. When they stop someone and suspect alcohol impairment, they ask for a breath sample using one of these portable devices.
PBTs are helpful for quick checks, but they are not always very accurate. Things like mouth alcohol contamination from recent alcohol consumption, breath fresheners, or even a burp can affect the reading. These devices are also more likely to give false results if not calibrated or used properly.
Because of this, the results from a PBT can be used in court only in limited ways. In many cases, the main reason police use this tool is to decide whether to arrest someone or continue with other tests. Remember that taking a PBT is usually part of a field sobriety test, and drivers often have the right to refuse it before arrest.
The second type of machine is used after someone has been arrested. It’s called an Evidential Breath Testing device, or EBT. These are larger, more advanced machines kept at police stations or testing centers. Unlike PBTs, EBTs are used to give an official reading of your blood alcohol concentration.
These machines are usually more accurate than portable devices. They are carefully checked and maintained to follow state rules. Some use fuel cell technology to find alcohol in your breath sample, while others use infrared light to measure how much alcohol is in your breath.
Because EBT results are considered more reliable, they are often used as main evidence in DUI cases. If your blood alcohol content (BAC) shows 0.08% or higher on this test, it could lead to charges—unless the machine was not working right, or something else affected the result.
That’s why Frances Prizzia Criminal Defense Lawyers always reviews how the test was given and whether the device was used properly in every case we take.
Breathalyzers do not look directly at your blood. Instead, they use special tools to measure the alcohol concentration in your breath. That number is used to guess your blood alcohol content (BAC) based on a set formula.
Breathalyzer machines use either a chemical reaction or infrared light to detect alcohol in your breath sample. These two methods work differently, but they both try to find out how much alcohol concentration is in the air you breathe out.
Some machines have a chamber with special chemicals that change color when alcohol is present. This change is used to calculate the blood alcohol content. Other machines use infrared light, which shines through your breath. The more light absorbed by the alcohol, the higher the reading on the screen.
Machines that use fuel cell technology are also common. These create electricity when they come into contact with breath alcohol, and that electric signal is used to measure your blood alcohol level. Police use all three methods depending on the device they carry or the one used at the station.
After you blow into the device, the machine quickly reads your breath sample and gives an estimated blood alcohol content (BAC) on a digital screen. This number is shown as a percentage -- for example, 0.08%.
This BAC number helps the police officer decide what to do next. If it shows that you are over the legal limit, you could be arrested and charged with DUI. For most drivers in California, the legal limit is 0.08%. For commercial drivers, it’s lower, and for drivers under 21, any alcohol present at all can be a problem.
Even though this number is just an estimate, many people are charged based on this one result. But things like mouth alcohol, medical conditions, and how the test was given can all affect the reading. That’s why your lawyer should always check how the test was done.
Breathalyzer machines are not always 100% correct. Many things can affect the results of a breath alcohol test. That’s why it’s best to understand what can go wrong during or before giving a breath sample.
Breathalyzer machines need to be checked often to make sure they are working correctly. This is called calibration, and it involves testing the device with a known alcohol concentration to see if it gives the right reading. If the machine is not calibrated the right way or at the right time, it may show the wrong blood alcohol level.
Also, like any other tool, these machines must be cleaned and cared for. If they are dirty, broken, or outdated, they can make mistakes. When a machine is not maintained properly, the numbers it gives can’t always be trusted. That’s why Frances Prizzia Criminal Defense Lawyers always check the service records of any breath test machine used in a case.
Sometimes, it’s not the machine that causes the mistake; it is the person using it. If the police officer giving the alcohol breath test doesn’t follow the correct steps, the result may not be valid. Officers must be trained to use the machine the right way. They also have to wait a certain amount of time after someone has been consuming alcohol before giving the test.
If the officer doesn’t follow those rules, like rushing the test, skipping a waiting period, or failing to watch the driver during the test, the breath sample result may be wrong. These kinds of mistakes are more common than people think. An experienced attorney will know how to spot them and use that information to help your defense.
Sometimes, there is extra alcohol in your mouth, not just in your lungs. This is called residual mouth alcohol, and it can come from many things. If you recently used mouthwash, drank alcohol just moments before the test, or burped before blowing, the machine might read that extra alcohol instead of the alcohol concentration in your deep lungs.
The problem is that the machine can’t always tell the difference between mouth alcohol contamination and real blood alcohol from your lungs. That’s why police are supposed to wait at least 15 minutes and make sure you haven’t eaten, burped, or used anything like breath fresheners before giving the test.
If they don’t wait, or if you still have alcohol present in your mouth, the reading could be too high. That’s another reason these tests can be challenged in court.
Some health problems can cause high breath alcohol readings, even when the person hasn’t had that much to drink. One example is GERD, a stomach condition where acid and gases come back up the throat. This can push alcohol concentration from the stomach into the mouth and lungs, which may confuse the machine and show a high blood alcohol content.
Diabetes can also be a problem. People with diabetes sometimes make chemicals in their body that can look like alcohol in a breath analyzer test. These false signals can trick the device and cause a reading that doesn’t match the person’s actual blood alcohol level.
That’s why injured victims or people with health issues should always tell their lawyer about any condition they have. It could help show that the test result was not accurate or should not be trusted.
Your blood alcohol content is always changing after you drink. Right after consuming alcohol, your BAC keeps rising for some time before it reaches its highest point. If a test is done too early, you might blow a result that looks legal. But if the test happens later, your BAC could be much higher, even if you weren’t over the legal limit while driving.
This is called the "rising BAC" defense. It means that even though your BAC was high during the test, it was still under the limit when you were behind the wheel. This matters in DUI cases because the law cares about your blood alcohol concentration at the time of driving, not at the time of testing.
An expert car accident attorney can use timing, receipts, witness statements, and expert reports to help prove that your BAC was still rising after you were pulled over.
If you are stopped for drunk driving in California, you still have rights. Police may ask you to take an alcohol breath test, but you don’t always have to say yes right away. Knowing your rights can help you protect yourself and avoid unfair treatment.
California has something called the Implied Consent Law. This means that if you drive in the state, you are agreeing to take a breath alcohol test, blood test, or urine test after being arrested for DUI. You don’t sign anything, but the law treats it like you already said “yes” just by driving on public roads.
If you refuse to give a breath sample after arrest, the DMV can suspend your license for one year or more, even if you weren’t drunk. Police may also use your refusal against you in court.
But this law only applies after you’re arrested, not before. That’s why the rules for preliminary alcohol screening are different, and you may have the right to say no before an arrest happens. It’s important to speak with a lawyer as soon as possible to understand what applies to your situation.
Type of Test | When It Happens | Can You Refuse It? | Used in Court? |
|---|---|---|---|
Preliminary Alcohol Screening (PAS) | Before Arrest (Roadside) | Usually Yes (for adults not on DUI probation) | Sometimes (for probable cause only) |
Post-Arrest Breath Test | After Arrest (At the station) | No (under Implied Consent Law) | Yes (used as DUI evidence) |
Knowing which test you're being asked to take is vital. It can affect your rights and what happens next in your case. A seasoned attorney can explain your options and defend you if your rights were violated during testing.
After you're arrested for DUI, you have the right to ask for a lawyer before answering any questions. Police may still ask you to give a breath sample, but they cannot stop you from talking to a lawyer after that test is done.
Even if you have already taken an alcohol breath test, your personal injury claim or DUI defense can still be helped by getting legal advice. An attorney can check whether the test was done the right way, whether your rights were respected, and whether the machine or officer made any mistakes that can be challenged in court.
1. Can breathalyzer results be wrong?
Yes. Breathalyzer machines can give incorrect results if they are not calibrated, used wrong, or affected by things like mouth alcohol, health problems, or even timing after alcohol consumption.
2. What is alcohol intoxication?
Alcohol intoxication means a person has too much alcohol in their body, which affects how they think, move, and make decisions. In driving cases, police use tests to check if someone is legally intoxicated.
3. Can I refuse a breathalyzer test in California?
You can refuse the preliminary alcohol screening (PAS) before you're arrested, unless you are under 21 or on DUI probation. But after you're arrested, refusing a breath sample can lead to serious penalties under the Implied Consent Law.
4. Is blood testing more accurate than a breath test?
A blood test often gives a more exact result than a breath alcohol test, but it also takes longer and must be handled carefully. Errors can still happen if the blood is not collected or stored correctly.
5. Can I still be arrested if my BAC is under 0.08%?
Yes. If police believe you showed signs of alcohol intoxication, like slurred speech or unsafe driving, they can arrest you even if your BAC is under the legal limit. That’s why having a lawyer is important.
If you’ve been arrested for DUI or asked to take a breath alcohol test, don’t wait to get legal help. Mistakes can happen with breath tests, and false readings can lead to unfair charges. You should not face the legal system alone, especially if you believe something about your breath sample or arrest was not right.
Frances Prizzia Criminal Defense Lawyers knows how to challenge test results, question the way tests were given, and protect your rights in court. We look at every detail, from the type of machine used to possible signs of alcohol intoxication that were recorded during the stop.
Call us today for a free consultation. We’ll listen to your story, answer your questions, and help you understand your options. There’s no cost to talk, and we’re ready to fight for you.
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