Posted by Gurjit Srai In DUI April 30, 2015 0 Comment

A police officer holding a breath test machine with his police car in the background. *the officer was blurred on purpose.

It is a common question asked by our clients charged with driving under the influence (DUI).  Are blood alcohol tests always accurate?  Is science totally reliable?

Blood Alcohol Testing Methods

In California, a blood alcohol content (BAC) reading over .08% is considered driving under the influence.  There are three basic ways to obtain BAC levels.  These include breath tests, blood samples, or urine specimens.


  • Breath tests:  When the police stop a motorist for suspected drunk driving, they may attempt to initiate a preliminary alcohol screening (PAS).    In many cases, a driver who has not been arrested may refuse to submit to a breathalyzer test without issue.  The two exceptions are:
    1. Drivers who are under age 21 and suspected of drunk driving
    2. Those on probation for another California DUI conviction

Refusal to submit to the breathalyzer test in either of the foregoing circumstances could result in a one-year license suspension.  There are also penalties for failing to submit to a breath test requested after arrest.  Even if the driver agreed to the PAS test, additional testing  will likely be required after the arrest.

  • Blood samples: Procedures for drawing blood to test BAC levels are outlined in Title 17 of California’s Code of Regulations.  Blood must be drawn in a hospital setting by trained personnel.  There are also requirements concerning sterilization to avoid contamination.  The law is quite strict as far as preserving blood samples.

Reliability of the Testing Methods

If your BAC level registers in excess of .08%, there is still the possibility that something went wrong with the manner in which it was tested.  SRAI Law considers the following when challenging testing methods:

  • How much experience did the person administering the test have?
  • Is there a question of accuracy with the machine used to take the breath test?  Was it properly calibrated and maintained?
  • What was the time lapse in procuring the breath, blood, or urine?
  • Did the defendant have other medical issues that might have contributed to an elevated reading?
  • Is there a chance the blood or urine samples were contaminated?
  • Was the chain of custody followed to maintain the integrity of the samples?

You Need Experienced Legal Advice

Driving under the influence is considered a criminal offense under California law.  Perhaps you have reason to suspect that your blood alcohol level was not accurate.  Even if this is not the case, you need solid legal advice.  Contact SRAI Law to make an appointment to discuss your defense of this very important matter.