The DWI statute in the Commonwealth of Pennsylvania establishes three levels of DWI offenses. There is a "loss of normal use" DWI that does not require the prosecution to prove an alcohol concentration (referred to as being incapable of safely driving). The state can also prove up general impairment by showing the driver had an alcohol concentration of between .08 and .10 within two hours of driving.
Should a driver have an alcohol concentration of between .10 and .15 within two hours of driving he can be charge with a "high rate of alcohol" DWI. Should that alcohol concentration be over .15, the driver can be charged with the "highest rate of alcohol" DWI.
The penalties for each of the three levels of offense get stiffer as the alcohol concentration rises.
In January 2010, Jason Schildt was arrested on suspicion of DWI when a police officer came across his car lying on its side in a ditch. A breath test on the state's Intoxilyzer 5000EN revealed an alcohol concentration of .20. Mr. Schildt was charged with multiple counts of driving while intoxicated and faced the most severe penalties as a result of his high breath test.
But, somewhere on the way to the plea docket, things got a bit hairy for the state.
Mr. Schildt's attorney filed a motion to quash the charge alleging that the state's breath test machine could not produce a reliable alcohol concentration reading over .015. The challenge was based on the initial calibration of the machine at the factory as well as the field calibrations conducted on the machines.
According to Pennsylvania regulations, the machine is supposed to be calibrated using simulator solutions purchased from an outside source and certified by an independent laboratory. At the hearing on the defense motion testimony from the state's "expert," an engineer at CMI, established that CMI, the manufacturer of the machine, performed the initial calibration of the machine using ethanol samples prepared in-house.
Furthermore, when the machines were calibrated in the field, they were only calibrated using ethanol solutions of .05, .10 and .15 concentrations. Another controversy arose about calibrating the machine to a zero point. Defense experts pointed out that for a machine to calibrate to zero would require it be able to distinguish a single atom. Anything else would be a guess. A true calibration curve only includes those data points established by a series of calibration tests - by "forcing" the calibration curve to cross the zero point, the curve below a .05 calibration was just pure speculation.
At the conclusion of the hearing, Court of Common Pleas Judge Lawrence Clark, Jr. found that the Intoxilyzers used by the Commonwealth could not be relied upon to produce a reliable result at alcohol concentrations below .05 or higher than .15.
The court did not find that the machines were unreliable - just that there was no scientific evidence that they could be relied up outside the range at which they were calibrated in the field. Judge Clark was also quick to point out that the defense was not challenging the regulations promulgated by the Commonwealth regarding the calibration of the machines. The challenge was to the conclusions made by the machine's keepers based upon the regulatory scheme.
The challenge was creative and illustrates why you have to know and understand the regulations surrounding breath test machines as well as how the machines operate in order to defend a drunk driving case properly. Over the years DWI laws have become more draconian and motorists' constitutional rights have been pared away. In that type of environment, sometimes the best defense is to know the minutiae of the machine better than the prosecutor.