The main difference in a field sobriety test vs. a breathalyzer is what each one measures and when police use it. A field sobriety test (FST) is a set of physical and attention tasks, like walking heel-to-toe or standing on one leg, that an officer uses at the roadside to look for signs of impairment. A breathalyzer is a device that measures the alcohol in your breath to estimate your blood alcohol concentration (BAC).
Washington drivers should also know that there are two types of breath tests. A roadside portable breath test (PBT) is voluntary, as are field sobriety tests. After an arrest, an evidentiary breath test falls under Washington’s implied consent law. Refusing that test can lead to a license revocation of at least one year. Veitch Ault Defense represents drivers facing DUI charges from its Bellevue and Lynnwood offices.
Key Takeaways
- Field sobriety tests measure behavior, while breathalyzers measure alcohol. An officer looks for physical clues during field tests. A breath test produces a number that estimates BAC.
- You can decline field sobriety tests in Washington. They are voluntary, and refusal does not cause an automatic driver’s license penalty. However, prosecutors may be able to use the refusal as evidence in court.
- The roadside breath test is voluntary; the post-arrest breath test falls under implied consent. Washington’s implied consent law, RCW 46.20.308, applies to an evidentiary breath test after arrest. Refusal can cause a license revocation of at least one year, and the refusal can be used at trial.
- Is it better to take a breathalyzer or a blood test for a DUI? Neither is always better. Each type of test has rules for how it must be collected, handled, and analyzed. Both can be reviewed for errors.
Is a Field Sobriety Test the Same as a Breathalyzer?
No. Police use these tests for different purposes and at different stages of a Washington DUI investigation. See the breakdown below:
|
Field sobriety tests |
Portable breath test (roadside) |
Evidentiary breath test (station) | |
|
What it measures |
Balance, coordination, eye movement, and ability to follow instructions |
Estimated breath alcohol |
Breath alcohol on a state-approved instrument |
|
When |
During the stop, before arrest |
During the stop, before arrest |
After arrest |
|
Required in WA? |
No |
No |
Implied consent applies |
|
Penalty for refusing |
No automatic license penalty |
No implied-consent license penalty |
1+ year revocation; refusal can be used at trial |
|
Main use |
Evidence supporting probable cause |
Evidence supporting probable cause |
Evidence of BAC |
Washington regulations specifically state that a preliminary breath test is voluntary and does not satisfy the implied consent law.
What Are the Standardized Field Sobriety Tests?
The National Highway Traffic Safety Administration (NHTSA) recognizes three standardized field sobriety tests:
- Horizontal gaze nystagmus (HGN): The officer watches the driver’s eyes while they follow a moving object and looks for certain types of involuntary jerking.
- Walk-and-turn: The driver takes nine heel-to-toe steps along a line, turns as instructed, and takes nine steps back.
- One-leg stand: The driver stands with one foot raised for about 30 seconds while counting aloud.
Police may also ask someone to recite the alphabet or count backward. Those tasks are not part of NHTSA’s three-test standardized battery.
What Fails a Field Sobriety Test?
There is no single act that automatically means a driver “failed.” Officers record specific clues during each test.
On the walk-and-turn, clues include starting too soon, missing heel-to-toe, stepping off the line, using the arms for balance, making the wrong turn, or taking the wrong number of steps. On the one-leg stand, an officer looks for swaying, raising the arms, hopping, or putting the foot down. NHTSA provides specific criteria for scoring these field sobriety test clues.
A sober person can also have trouble with these tasks. Injuries, fatigue, nerves, age, physical limitations, footwear, weather, and an uneven testing surface may affect performance.
Why Do Cops Do Field Sobriety Tests Instead of a Breathalyzer?
Police use field sobriety tests to gather observations that may help establish probable cause for a DUI arrest. An officer can describe how a driver followed directions, walked, balanced, or moved their eyes.
A roadside PBT can also help establish probable cause, but Washington rules say its result cannot, by itself, prove beyond a reasonable doubt that a driver’s BAC exceeded the legal limit. Breath testing also only measures alcohol rather than other drugs, such as cannabis. An evidentiary breath test or, in some cases, a blood test generally comes after an arrest.
Can You Take a Breathalyzer Instead of a Field Sobriety Test?
A driver cannot require an officer to substitute a breath test for field sobriety tests. In Washington, a driver may decline both the field sobriety tests and the roadside PBT.
Note that this does not prevent an arrest. An officer may rely on driving behavior, speech, appearance, odors, statements, physical actions, and other observations when deciding whether there is probable cause for an arrest.
Should I Refuse a Field Sobriety Test If I’m Sober?
Washington courts describe field sobriety tests as voluntary. There is no automatic Department of Licensing penalty for declining them. However, refusal does not guarantee that a driver will avoid arrest, and Washington courts have allowed evidence of an FST refusal to be used at trial.
The tests can also be affected by physical conditions and the setting in which they are given. Whether to take or refuse a test depends on the facts of the stop. This information is general and is not legal advice for your specific situation.
Is It Better to Take a Breathalyzer or a Blood Test for a DUI?
Neither test is always better. They measure and collect evidence in different ways.
A breath test is fast and measures alcohol in a person’s breath. Its reliability may depend on factors such as the required observation period, possible mouth alcohol, the condition and maintenance of the instrument, and whether testing rules were followed. Washington law sets detailed requirements for an evidentiary breath test.
Blood testing can measure alcohol and drugs, including THC. Police may obtain blood under a search warrant or another lawful exception listed in RCW 46.20.308. A defense review may examine the blood draw, labeling, storage, chain of custody, and laboratory analysis.
Washington law also allows a person who was tested to obtain an additional test from a qualified person of their choosing.
Can You Refuse a Breathalyzer in Washington State?
You can refuse a breathalyzer in Washington State, but refusing the evidentiary breath test after arrest has serious consequences.
Before that test, an officer must give the warnings required by Washington’s implied consent law. Those warnings explain the consequences of refusing.
- Your license can be revoked. Under RCW 46.20.3101, a first refusal with no qualifying prior incident within seven years results in a one-year revocation. A second or later refusal within seven years, or a first refusal with a qualifying prior administrative incident, results in a two-year revocation.
- The refusal may be used in a criminal trial. Washington law requires police to warn drivers about this consequence before requesting the evidentiary breath test.
- Police may seek blood evidence. RCW 46.20.308 allows police to obtain blood under a search warrant, a valid exception to the warrant requirement, exigent circumstances, or other lawful authority.
These rules are different from the roadside PBT. Under WAC 448-15-020, the PBT is voluntary and is separate from Washington’s implied consent process.
How Veitch Ault Defense Challenges Sobriety Tests
A DUI test result should be reviewed in the context of the full stop. Veitch Ault Defense examines how field sobriety tests were explained and given, what the officer recorded, whether breath-testing rules were followed, and whether the state can establish the required foundation for its evidence.
Our DUI defense experience includes NHTSA training in DWI Detection/Standardized Field Sobriety Testing and Advanced Roadside Impairment Detection Enforcement (ARIDE). Our attorneys can also review instrument records, maintenance issues, and possible violations of a driver’s rights. We can’t promise a particular outcome, but we can identify the issues that may affect the state’s case.
Frequently Asked Questions
Are field sobriety tests mandatory in Washington?
No. Washington courts have described field sobriety tests as voluntary. A driver who declines them can still be arrested based on other evidence, and the refusal itself may be admissible at trial. The Washington Supreme Court addressed the use of FST refusal evidence in City of Seattle v. Stalsbroten and later cases.
What breath test machine does Washington use?
The Washington State Patrol Breath Test Program uses the Dräger Alcotest 9510 for evidentiary breath alcohol testing. Washington’s testing protocol calls for at least two breath samples. State law also sets standards for the samples and other parts of the test.
How long is your license suspended for refusing a breath test in Washington?
Technically, Washington law calls the administrative penalty for refusal a revocation. For a first refusal with no qualifying prior incident within seven years, the revocation is one year. A second or later refusal within seven years, or a first refusal when there has been a qualifying prior administrative incident, results in a two-year revocation under RCW 46.20.3101.
Can field sobriety tests detect drugs?
Field sobriety tests can give an officer observations that may be consistent with impairment, but the standard tests do not identify which substance a person has used. A breath test measures alcohol and does not measure THC. When police seek chemical evidence of cannabis or another drug, they may seek a blood test under lawful authority.
Talk to a Washington DUI Attorney About Your Test Results
The details matter when a DUI case involves field sobriety, breath, or blood testing, and Veitch Ault Defense can review what happened during your stop and arrest. Call 425-452-1600 for a free consultation with a Washington DUI attorney.