Understanding Breath and Blood Tests in Washington DUI Cases
If you’re stopped for suspected DUI in Washington, officers can use different chemical tests to measure alcohol or drug levels in your body. Knowing which tests are voluntary, which are required, and what happens if you refuse is critical to protecting your license and your rights.
The Two Main Types of DUI Tests in Washington
1. Preliminary (Portable) Breath Test – Voluntary
During a roadside stop, officers may ask you to take a Preliminary Breath Test (PBT) using a handheld device. This test estimates your breath alcohol concentration and helps officers decide whether to arrest you.
However, a PBT is not legally admissible in trial because it’s less accurate than station-based devices. It’s considered a screening tool, not an evidentiary test.
Key points:
- You are not required to take a PBT.
- Politely declining a PBT does not result in license suspension or administrative penalties.
- The officer can still arrest you based on other evidence (such as odor, slurred speech, or failed field sobriety tests).
If you agree to a PBT and the reading is low (for example, below 0.04%), you may not be arrested. If it’s higher, the officer will likely continue investigating and may arrest you for DUI.
2. Evidentiary Breath Test – Required After Arrest
Once you’re arrested for DUI, you’ll be asked to take a station breath test (using a DataMaster or similar machine). This test is admissible in court and is used to determine your official Blood Alcohol Concentration (BAC).
Before the test, the officer must read you Washington’s Implied Consent Warnings, which explain:
- You have the right to refuse the test.
- Refusal will lead to a one year revocation of your license.
- Test results of 0.08% or higher create a presumption of impairment under RCW 46.61.502.
- You have the right to speak to an attorney before deciding.
In short:
- Refusing the evidentiary test has serious administrative consequences.
- Taking it may provide evidence against you, but refusal guarantees penalties.
- A defense lawyer can challenge test procedures later if errors occurred.
When Blood Tests Are Used
Blood draws are generally reserved for special circumstances:
- The driver is suspected of drug or marijuana impairment, not alcohol.
- The driver is injured, unconscious, or medically unable to perform a breath test.
- The driver refuses a breath test, and the officer obtains a search warrant for a blood sample.
Under RCW 46.20.308, officers can request a warrant-supported blood draw if they establish probable cause. Refusing a warranted blood test can lead to additional criminal charges for obstruction or contempt.
When Should You Take or Refuse a Test?
There is no universal answer—it depends on your situation. Here’s what to consider:
You may consider taking the evidentiary test if:
- You believe you’re well below the legal limit.
- It’s your first alleged offense, and you want to avoid the one-year refusal revocation.
- You want to show cooperation and reduce administrative penalties.
You may consider refusing if:
- This is not your first DUI.
- You want to limit the prosecution’s evidence, understanding your license will still be suspended.
- You plan to contest the suspension with an attorney through the Department of Licensing hearing.
Either way, speak with a DUI attorney immediately—you are entitled to legal advice before deciding. The attorney can explain both the criminal and administrative consequences in real time.
Implied Consent and Your License
Washington’s Implied Consent Law means that by driving on state roads, you’ve already consented to breath or blood testing if lawfully arrested for DUI. Refusal doesn’t avoid consequences—it simply changes them:
- Refusal: Suspension (1–2 years) and possible ignition interlock requirement.
- Failure (0.08%+): Shorter suspension (90 days for first offense), but still subject to criminal penalties.
You have seven days after a refusal or a breath test of over 0.08% to request a hearing with the Department of Licensing (DOL) to contest the suspension.
How Attorneys Challenge Breath and Blood Tests
A DUI defense lawyer can examine:
- Whether implied consent warnings were properly read.
- Did the officer misstate the warnings? (e.g., providing incorrect information about penalties).
- If the driver expressed confusion.
- The timing of the test relative to driving.
- Whether the DataMaster machine was correctly calibrated.
- How the blood sample was stored, transported, and analyzed.
- Whether the warrant for a blood draw met legal standards.
These technical details often determine whether evidence can be suppressed or a case dismissed.
Key Takeaways
- All roadside portable breath tests are voluntary and non-evidentiary.
- The station breath test (DataMaster) is evidentiary; refusal triggers license revocation.
- Blood tests are used when breath tests aren’t possible or when drugs are suspected.
- Consult an attorney before deciding whether to take or refuse a test.
- The decision affects both your criminal case and driver’s license separately.