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Radio Frequency Can Cause Falsely High Breath Test Results

by ptbarone on December 21, 2009

In reviewing videotapes of our client’s DUI arrests we often see cell phones being used in the booking room at the same time that the breath test is being administered.  The problem is that cell phones create radio waves, and these waves can interfere with the breath test.  Here is a videotape regarding this problem.  The videotape addresses the Intoxilyzer.  In Michigan we use the DataMaster, but the underlying concepts are the same.


Today cell phones are ubiquitous, and it is not unusual to see them in and around the breath testing equipment.  The prohibition against using portable radio transmitters, including cell phones, is grounded in well-known limitations in infrared breath testing technology. 

The problem originally dates back to 1982, when “Smith & Wesson, a major manufacturer of breath-testing devices, notified law enforcement agencies that its Breathalyzer Model 1000 had been found to experience interference from radio frequency transmissions under certain test conditions, resulting in false test results.  Subsequent investigation suggested that the Breathalyzer Models 900 and 900A also were affected by various power levels.”[i] 

But the problem of radio frequency interference didn’t go away with better more modern equipment. Such breath testing equipment typically has RFI detectors incorporated within them.  The problem with these detectors is that they are not predictable.  Thus, it is impossible in many cases to determine whether or to what extent any particular breath test was tainted. With an instrument such as the Breathalyzer, where someone’s rights and freedoms are at stake, unpredictable performance is unacceptable.”[ii]   And, according to at least one source, RFI can potentially lead to breath test scores inflated by as much as 100%.[iii]             

Additionally, as repeated tests have demonstrated, there is a segment of the frequency band to which the detector is essentially blind.  If there is a source of interference from a device emitting electromagnetic waves in this frequency range, it will not be detected.[iv]

Manufacturers and state experts will often point to the infalability of the RFI detectors that exist in modern breath testing equipment.  The problem is that, like slope detectors, and as shown by Mr. Biss in the video above, RFI detectors don’t work.  Thus, the incorporation of the RFI detector does not necessarily ensure that the breath testing equipment will be protected from RFI.  In order to pick up radio waves, the antenna connected to the RFI detector must be oriented in the proper position. 

This situation can best be understood if one thinks about trying to pick up a station with an old fashioned portable radio or a television station with the new digital tuners.  It is important for the antenna of the radio or television to be oriented in the right position to receive the desired station.  Thus, even though the RFI detector may be capable of sensing RFI, the electronic circuitry of the particular breath testing machine could possibly be located in a position that it will not pick up the existing radio waves.[v]   

Contact the Barone Defense Firm today to discuss whether or not RFI may have caused a false result in your drunk driving case.

[i] Lawrence Taylor, Drunk Driving Defense § 6.04[J] (6th ed.) (2006).

[ii] Feldman and Cohen, “The Questionable Accuracy of Breathalyzer Tests,” 19 Trial 6, 54 (1983). Excerpted from: Patrick T. Barone, Defending Drinking Drivers § 226 (2nd ed.) (2009)

[iii] See, Paul Schop, Is DWI DOA?: Admissibility of Breath Testing Evidence in the Wake of Recent Challenges to Breath Testing Devices, 20 SW. U. L. REV. 247 n.22 (1991)

[iv] Lawrence Taylor, Drunk Driving Defense § 6.04[J] (6th ed.) (2006).

[v] Don Nichols and Flem Whited, Drinking/Driving Litigation Criminal and Civil, § 22:8 (2nd ed.1998).


{ 2 comments… read them below or add one }

Chuck Ramsay December 22, 2009 at 3:07 am

This is the best blog posting I've seen on this flaw in breath testing machines. Well done. So many lawyers just assume the RFI detector works properly all the time. You article helps to educate the public, judges and prosecutors. Thank you.


pbarone December 22, 2009 at 12:27 pm

Re: Michigan DUI Help – New comment requires moderation on: Radio Frequency Can Cause Falsely High Breath Test Results



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