Radio Frequencies Can Interfere with a DUI Breath Test


I’ve said it before and I’ll say it again: Breathalyzers are inaccurate. One of the lesser known causes of breath test error is radio frequency interference (RFI).

Unlike a blood test, the most common breathalyzers use infrared spectroscopy to determine a DUI suspect’s blood alcohol content level. Electromagnetic or electrochemical technology allows the machine to read energy wavelengths which convey the alcohol content in a person’s breath. The breathalyzer then converts the breath alcohol into blood alcohol using a mathematical equation.

This process can be disrupted because breathalyzers can pick up radio frequencies from certain devices. Devices which emit radio frequency interference, sometimes called electromagnetic interference (EMI), include, but are not limited to cell phones, police radios, AM and FM radios, fluorescent lights, fax machines, walkie-talkies, security cameras, and microwaves.

Is the government aware that this problem exists? You bet.

In 1983, the National Bureau of Standards prepared a report entitled “Effects for the Electromagnetic Fields on Evidential Breath Testers.” The report found that of the 16 models that were tested, six experienced minimal radio frequency interference. However, the remaining ten modes experienced substantial interference. As a result, the drafters of the report characterized the effect of radio frequency interference as “severe.”

In response, manufacturers began developing and distributing “RFI” detectors. While prosecutors often point to these detectors to refute the presence of radio frequency interference, these detectors, like breathalyzers themselves, are inaccurate.

Think about the settings in which people blow into breathalyzers. Were any of the aforementioned radio frequency-emitting devices present? Quite possibly.

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