In Michigan, police officers use the Datamaster machine to test breath samples; this device is electronic and subject to the same interference as other devices that generate electrical power. One kind of interference that is possible is radio frequency interference or RFI.
Although the machine apparently has a built in sensor, which is designed to seek and identify this sort of interference, there is no guideline or information about how sensitive the sensor actually is during the tests. Just like a metal detector; some may pick up the metal on your belt, and some may not, but we all know there is metal being undetected. The same holds true for radio interference; we know there are radios in and around a police station, potentially even right next to the device if the officer has one; if the sensor doesn’t go off, does that actually mean something? It’s my position that there is always the possibility of some radio interference, even if the sensor does not pick it up.
In my experience there are at least five types of radio interference that must be detected, many which may not be picked up with a low sensitivity sensor. It’s imperative to test for radio interference from mobile transmitters from patrol cars, ambulances and fire trucks, even news trucks driving around and private citizens using them. It must test for military and private security radio, base radio communication from the police station itself, portable transmitters from handheld police radios and a scenario where all of them are acting in concert.
It’s not a stretch to have a situation where the police station is surrounded by private citizens transmitting radio signals, military operations being conducted in the airspace, each cop having his own radio on his person, multiple police cars, and emergency vehicles transmitting and the police station itself (where the test is being conducted) sending out various signals to those same cars and officers.
Many prosecutors, police officers and judges roll their eyes at radio interference, and I really don’t quite understand why? It’s likely that the attorney presenting it moved on too quick without having the witness acknowledge all the possibilities, and the fact that we have no idea how sensitive the device actually is or isn’t.
Another problem area, which goes unchallenged is the machine only conducts a test at the very beginning; some of these tests take 10 to 15 minutes. Radio waves come and go, especially at a busy police station, and to simply ignore further tests is absurd. Some states have acknowledged this gap by placing shields on the device, but Michigan has not done so, which is an excellent issue to put in front of a jury to challenge the test results. In my view, until a shield is adopted by Michigan then no Datamaster test is actually fully reliable; how can a jury believe beyond a reasonable doubt that the test was accurate when a neighboring state doubted their same tests, and added the extra precaution.