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Expert Witnesses in DUI Cases

Expert witness testimony can often be the key to acquittal on California DUI charges.

Prosecutors investigate, develop and emphasize aspects of a DUI case so as to obtain a conviction. And while they are obligated to provide defendants with evidence that would tend to exonerate them, it's not the prosecutor's job to go looking for it. A defendant facing a DUI charge, therefore, would do well to hire his or her own expert witness.

1. Why Do I Need an Expert Witness?

In many California DUI cases, an expert witness is not required.  But when it comes to testimony about DUI, juries often give extra weight to the opinions of people with specialized training in fields such as:

  • chemistry,
  • medicine,
  • brain science, or
  • accident reconstruction.

2. How Can an Expert Witness Help My California DUI Case?

A DUI defense expert can:

  • challenge the arresting officer's conclusion that you were under the influence -- often using the officer's own report;
  • refute the conclusions of the prosecution's expert witnesses;
  • demonstrate how your performance on field sobriety tests fails to show impairment;
  • identify flaws in your DUI blood and/or breath chemical tests; and/or
  • provide valid scientific reasons why the results of such tests are not reliable evidence of intoxication.

An expert's evidence could well be the key to your acquittal.  Just as importantly, it might convince the prosecutor to reduce the DUI charges -- or even dismiss them -- before your case ever goes to trial.

An expert can prove useful even when there is no evidence of problems with your chemical test.  If your blood alcohol content ("BAC") is close to the legal limit of .08%, an expert can testify that DUI test results have an inherent margin of error.  Sometimes, that is all the reasonable doubt that is needed.

3. How Much Does a California DUI Expert Witness Cost?

Expert witnesses can cost as much as $450-$2,000 a day, depending on the services being provided. Testifying usually costs more than reviewing your file.

But conviction on a DUI can cost you that much in fines. Worse, you could also face:

  • suspension or revocation of your driver's license,
  • three to five years probation (for a first offense), and
  • time in county jail.

Our Southern California DUI lawyers know how to work with expert witnesses. We understand how to maximize their benefits and minimize their costs. Expert witnesses in California DUI cases are able to undo the prosecution's case more often than you might imagine. We see it happen all the time.

Expert witnesses are just one tool for fighting DUI in California. If you have been accused of DUI, we invite you to contact us for a free consultation. We represent clients throughout Los Angeles, Orange, San Bernardino and Riverside Counties. You can fight back.

Southern California DUI Defense


DUI cases are rarely hopeless. DUI convictions are almost never inevitable. Clients retain our California DUI defense attorneys for one reason: they want to fight the case. And win.

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The police arrested you for DUI. You gave a blood or a breath sample. The DUI officer confiscated you drivers license. The police released you with a notice to appear in court in a few weeks. Where do you go from here? Our lawyers are here to guide you step by step.