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RFI (Radio Frequency Interference) in California DUI Breath Tests

Don't just let your DUI breath test convince you that your case is lost.  Talk to an experienced California DUI lawyer to see if RFI may have compromised the results.

Most California DUI arrests and prosecutions depend on evidence of a person's blood alcohol content (BAC). In California, this evidence is usually obtained from a DUI breath test.

1. How DUI Breath Machines Work

Unlike DUI blood tests -- which measure alcohol in the blood directly -- breath testing machines use electromagnetic or electrochemical technologies such as infrared spectroscopy. These machines measure the alcohol in a breath sample and convert it mathematically to a BAC equivalent.

2. RFI Can Intefere with DUI Breath Testing Accuracy

DUI breath machines can "pick up" radio frequencies sent out by other devices. These other frequencies then interfere with the accuracy of the machine's BAC readings.

Devices that produce such radio frequency interference (RFI) include:

  • cell phones,
  • radio transmitters,
  • refrigerators, and
  • microwave ovens.

Any of these devices could be could be nearby when officers are taking a DUI suspect's breath sample. The officer might not even know it.

RFI can cause a breath testing machine to determine wrongly that:

Our Los Angeles DUI Lawyers have seen radio frequency interference lead to wrongful DUI arrests and charges. Fortunately, we know how to find it. Once the prosecutor realizes that the breath test evidence in a case is faulty, he or she will often reduce the charges... or drop them altogether.

We have offices throughout Los Angeles, Orange, Ventura, San Bernardino and Riverside Counties. Contact us today for a free consultation to discover your best California DUI defense.

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.