The recent court case of a British aristocrat with close ties to Princes William and Harry has once again highlighted the issue of breathalyzer radio frequency interference.
Nightclub owner Guy Pelly was pulled over while driving his Audi R8 GT V10 Coupe through central London last May after reportedly visiting one of his exclusive clubs. The 32-year-old reportedly refused to submit to a roadside breathalyzer test, later claiming he “panicked” because he knew he was close to the legal limit, and was subsequently taken to Belgravia Police Station to be tested using a more complex machine.
At Pelly’s trial last week, lawyers alleged radio waves from his iPhone may have interfered with the station’s intoxicometer, resulting in a false reading. No supporting evidence thus far has been released publicly.
The susceptibility of breathalyzers to RF interference is not a new concept. According to a preliminary report of test results for EMI released by the National Bureau of Standards (NBS) in 1983, eight of 16 evidential breath tester (EBT) units evaluated showed potential EMI problems under the specific test conditions of nominal 10 volts per meter electric field strength.
“It is apparent that EMI manifests itself in several ways depending upon the individual EBT instrument being tested,” the report stated. “The average alcohol vapor concentration reading may increase or decrease in the presence of an EM field and, in some cases, the EBT may blank the display, set an error flag, or cease operation. It is also clear that the orientation of the EBT within the EM field influences the extent to which the energy within the field is coupled into the EBT.”
However, the report cautions, “the data [is] too limited to permit the extrapolation of potential EMI susceptibility to frequencies other than those specifically used during the tests.” In most cases, the tests were conducted on single units and at single frequencies in the public-safety radio service band.
In addition, the fields “selected for the tests are based on line of sight transmission and do not take into account either attenuation from structures that surround EBTs in use, or possible multipath perturbations from such structures or their surrounding environment.”
The measurements were also conducted in a laboratory setting, meaning they are not representative of specific environments that may be encountered by law enforcement using the devices in question.
While the question of whether Pelly’s iPhone interfered with an accurate BAC reading remains thus far unanswered, it could lend itself to an arguement that more research is needed into the effects of EMI on breathalyzers, especially in the context of new technology such as smartphones.
What do you think?
