5 Things You Should Know About DUI Blood Tests in California

DUI Defense Guide

In California there is an implied consent law that states that all drivers give their implied consent to a DUI chemical test just by driving in the state

In Our FAQ's To DUI Blood Test Laws We'll Cover:

  1. Can An Attorney Challenge a DUI Blood Test?
  2. Can A Different Lab Test My Blood?
  3. Will An Alcohol Swab Affect The Test Results?
  4. Are Blood Tests Reliable?
  5. Do Most People Refuse To Take The Blood Test?


In California, a person can be arrested for DUI if they are found driving with a blood alcohol content (BAC) of 0.08% or greater. In general, a warrant is necessary for the police to draw someone’s blood after they have been arrested for DUI and then test the blood to obtain the person’s BAC at the time they were driving.

If a driver refuses a DUI blood test in California, they will get their driver’s license suspended. If a driver is stopped for DUI, they are usually given field sobriety tests. If the driver fails these tests, they may be taken to a hospital to get a DUI blood test.  Under Title 17 of the California Code of Regulations, DUI blood tests must be performed by a trained technician who uses proper medical practices for the results of the blood test to be admissible against someone later in court.

DUI Blood Test Frequently Asked Questions

1. Can An Attorney Challenge a DUI Blood Test?

dui blood test in lab

Yes. An experienced DUI attorney can challenge a DUI blood test in your case because even toxicologists cannot always be certain that a driver’s BAC was above or below a particular limit. There is usually a variance of 3%-10% within where a driver’s actual BAC was when they were driving. This means that even though you might have tested at 0.08%, your actual BAC when you were driving might have really been only 0.04%.

2. Can I Have Another Laboratory Test My Blood To Find Out My BAC?

Yes. In California, your DUI attorney can usually file a motion with the court to get your blood sample tested by an independent laboratory.

3. If The Medical Technician Uses An Alcohol Swab On Me Before The Blood Test, Will This Affect the Test Results?

Yes. This can contaminate your blood sample because alcohol swabs usually contain 2% ethyl alcohol.

4. Are DUI Blood Tests Even Reliable?

DUI blood tests are generally thought to be reliable since the evidence (i.e. blood sample) can be re-analyzed at a later date. However, a problem with the reliability of DUI blood tests is that lab testing errors may throw off the results of the tests in some cases. Some lab testing errors can throw off final blood-alcohol readings by .001 percentage points and this can cause people to be wrongly identified as having an excessively high BAC when their blood-alcohol level really wasn’t that high.

5. Do Most People Refuse To Take DUI Blood Tests?

No. Most people agree to have a DUI blood test because they will face additional penalties under the implied consent law if they refuse to take the test. Also, if a person refuses to take a DUI blood test, the prosecutor in the case can try to use their refusal as evidence of their guilt.

Title 17 Blood Test Requirements

You have the option of taking a breath or blood test if you are suspected of driving while under the influence of alcohol. In most cases, you will be required to first take the breath test and then be given the option of taking a blood test at no cost to you1.

If a breathalyzer is broken or unavailable, then you must submit to blood testing or be considered to have refused testing. There is an exception for hemophiliacs or for individuals who take coagulants for a heart condition. In these cases, they are not required to take a blood test.

If the officer suspects you of driving impaired due to drugs, then you will be asked to submit to a blood test since the breath test will not detect the presence of drugs other than alcohol. For blood test draws, here are certain procedures that officers and technicians must follow under Title 17:

  • The test must be administered by a trained technician
  • Your blood must be placed in a vial that contains certain amounts of anti-coagulant to prevent clotting and preservative to prevent its spoilage.
  • The anti-coagulant and preservative must meet expiration dates
  • The technician must not swab your skin with an alcohol-based substance before drawing the blood sample
  • Your blood sample must be properly mixed with the anti-coagulant and preservative
  • The blood sample is to be properly marked for identification and stored
  • Your blood sample must be kept for one year

Hiring An Attorney

At the Aizman Law Firm, a Los Angeles DUI attorney can help you with questions you might have about whether the results of your DUI blood test were reliable. If you need to speak to an attorney about your case please call our office at: (818) 351-9555.

Request A Free Consultation 818-351-9555 


  1. California v. Trombetta (1984) 467 US 479 []

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