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What Is a Chemical Test for DUI Cases Under California Law?

Writer's picture: Blair GossBlair Goss

When a driver is suspected of driving under the influence (DUI), California law requires enforcement agents to conduct a "chemical test."


This could be a breath test, blood draw, or even a urine test. Each option serves a specific purpose in helping to measure the driver’s blood alcohol content (BAC) and determine if they’re over the legal limit.


Knowing what to expect and how each test works can be helpful for drivers who want to understand their rights and responsibilities in a DUI situation. Knowing what happens if you get a dui in another state can be important information.


What Are the Three Types of Chemical Testing in DUI Arrests?

What Are the Three Types of Chemical Testing in DUI Arrests?


Police officers use three main types of chemical testing for DUI cases: breath, blood, and urine tests. For more information, a quality DUI lawyer may be able to help. However, each screening works differently and has unique strengths and limitations.


Breath Test

One of the most commonly used DUI tests in California is the breath test. When law enforcement suspects a driver of DUI, they might start with a roadside breath test, also known as a preliminary alcohol screening (PAS test). Our team can advise on what is the punishment for first dui in California.


This preliminary breath test uses a handheld device to measure BAC, giving officers a quick readout. If a driver’s BAC is over the legal limit (0.08% for most drivers), it could lead to a DUI arrest.


After a DUI arrest, the police may administer a more thorough breath test at the police station. Known as "evidential" breath testing, this version is usually more reliable than the PAS test.


Breath tests work well because they’re fast and relatively non-invasive. However, they aren’t perfect - factors like the driver’s health, recent food intake, and even certain medical conditions can affect results.


Blood Test

When accuracy is crucial, police often turn to blood tests. Such a method involves taking a blood sample, which is later analyzed to determine the exact BAC.


This technique is very reliable, as it directly measures alcohol in the bloodstream. Blood tests are also useful when drugs other than alcohol are suspected in a DUI case.


While effective, blood tests are more invasive and require a professional to draw the blood sample. They’re usually done at a police station or a hospital after the driver is taken in.


The downside is that it takes longer to process and requires more care to ensure proper handling of the blood sample.


As a result, a blood test is typically reserved for situations where other methods may be impractical or unclear.


Urine Test

Urine tests are the least common of the DUI chemical screenings in California.


Such a method is typically only used when neither a breath nor a blood test is available or if there’s a medical reason the driver can’t take either of those options.


Urine tests aren’t as precise as blood or breath testing, but they’re still legally valid under California law in certain situations.


How Accurate Are DUI Chemical Tests?


Chemical tests in drunk driving cases are quite accurate but not flawless. Each type has its limitations.


For example, breath tests can be affected by outside factors like mouthwash, certain diets, or even a driver’s medical conditions.


Blood draws, while highly accurate, can be mishandled, resulting in possible contamination of the blood sample.


Meanwhile, urine tests are generally less reliable and not commonly used due to issues with accuracy. Such methods check the alcohol level in water instead of blood, making it highly diluted.

Understanding "Implied Consent" in Chemical Testing


California has an “implied consent” law, which means that by driving in the state, motorists agree to take a chemical test if law enforcement suspects them of driving under the influence of alcohol or drugs.


A chemical test refusal can lead to severe consequences, including an automatic license suspension and other penalties, even if the driver wasn’t intoxicated.


Implied consent applies to breath and blood tests after a DUI arrest, so automobilists need to understand this responsibility.


Can the Convicted Choose Between a Breath or Blood Test?


When arrested for drunk driving, drivers are usually given two main options: a breath or a blood test.

This choice is often offered because each method has different benefits. Breath tests are quick and convenient, while blood draws are generally more accurate.


However, there are limits to this choice. If officers suspect the driver may have drugs in their system rather than alcohol, the motorist may not have a choice since a blood test is more suitable for drug detection.


Additionally, the choice might be influenced by the setting. Breath tests are often done at the police station or in the field, while blood tests typically require a hospital or trained medical professional.


When Is a Driver Denied Choice?


One common scenario is when someone is suspected of driving under the influence of drugs rather than alcohol. Since breath tests can’t detect drugs, the driver will be required to take a blood test.


Another situation where the choice is limited is if one of the testing methods is unavailable.


If a breath test machine is broken or there’s no one trained to take a blood specimen, the driver will need to take the available option.


Officers also have discretion if they believe one method is necessary over another based on the situation.


Are DUI Chemical Tests Different from Breathalyzer Tests?

Are DUI Chemical Tests Different from Breathalyzer Tests?


The main difference between chemical testing and breathalyzer tests is scope.


While all breathalyzer tests are chemical screenings, the same cannot be said for all tests.


A chemical test covers three types of examinations: breath, blood, and urine examinations. Each type serves the same purpose - checking BAC - but they work in different ways:


  • Breath tests are fast, non-invasive, and give instant results. They are common because they’re easy to perform during a traffic stop. However, they’re not as accurate as blood tests.

  • Forensic blood tests can measure alcohol directly in the bloodstream, making them more accurate than breath tests. These are usually performed at a hospital or police station and can detect drugs as well. However, blood examinations are invasive and take longer to process.

  • Urine tests are rarely used for alcohol detection but can detect drugs if breath or blood tests aren’t possible. These tests are less reliable than breath or blood tests, which is why they’re only used in special situations.


Final Words


Chemical tests are a key part of enforcing DUI laws and keeping the roads safe.


From breath tests at the roadside to blood and urine tests for more detailed analysis, these methods play an essential role in determining whether a driver is under the influence.


Refusing a test comes with serious consequences, like automatic license suspension and even potential jail time. The qualified attorneys at Goss Law can represent wrongly convicted drivers in court and fight for their rights.


In the end, the best choice is always to drive sober and avoid risking it altogether.

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