EvidenceProf Blog

Editor: Colin Miller
Univ. of South Carolina School of Law

Friday, March 21, 2008

Device Under The Influence: Illinois Judge Finds Passive Alcohol Sensor Can Be Used To Gain Probable Cause

Last week, Kane County Judge Allen Anderson became the first Illinois judge to hold that the PAS IV, a passive alcohol sensor, can be used to put a suspected drunk driver through sobriety tests.  Several Kane County, Illinois police departments use the PAS IV during traffic stops.  The sensor looks like a heavy duty flashlight, but it uses a small intake valve to measure alcohol in the air. When alcohol is detected on a fuel cell, it lights up the PAS IV device.  The device is useful because a police officer might be talking with a motorist he or she instinctively believes has been consuming alcoholic beverages, but the officer is unable to establish probable cause.  An officer equipped with the PAS IV can hold it in close proximity to the vehicle, and by taking a sample of air the PAS IV is able to detect the presence of alcohol either on the driver’s breath or within the vehicle with an alleged 97 percent accuracy rate.

The driver does not need to blow into the device; instead, the device draws in air through a port and past a fuel cell, which will generate a small electric current if alcohol vapor is present. The current is amplified electronically and becomes visible on a display on the outside of the device.  Judge Anderson agreed with the argument of Kane County Assistant State's Attorney Steve Sims that the fuel cell technology is not new and that the U.S. Department of Transportation evaluated an earlier model of the passive alcohol sensor and determined it to be reliable.  He thus ruled that the PAS IV can be used to gain the probable cause necessary to conduct sobriety tests even though it does not provide a blood alcohol reading.

All of this makes sense to me because it seems that the PAS IV is reliable enough to meet the probable cause standard in that its results would warrant a prudent person's belief that the driver had committed a crime.  But the article on the case (I don't have access to the opinion) indicates that "Judge Allen Anderson had to determine whether the scientific principles behind the technology are sufficiently established to have gained general acceptance."  This is the Frye test for determining whether expert evidence is admissible at trial, but it is well established that the rules of evidence do not need to be applied to determine whether probable cause exists. See e.g., Brinegar v. United States, 338 U.S. 160, 174 n.12 (1949).  In other words, a police officer can develop probable cause from evidence which would be inadmissible at a subsequent trial.  I thus see no reason why Judge Anderson should have applied the Frye test to the PAS IV, but maybe something was lost in translation to the article.



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