The Insurance Institute for Highway Safety is a nonprofit research organization dedicated to finding and evaluating methods to reduce the deaths and injuries that result from motor vehicle crashes. The Institute is supported wholly by the nation's property and casualty insurers. The Institute does not have any financial interest in any products, nor does it endorse specific products.

The Institute was instrumental in the late 1970s in developing prototype passive alcohol sensors (PAS) and has conducted extensive research on their effectiveness both in the laboratory and in the field.

Two legal issues that come to mind with regard to any new law enforcement technology are reliability and constitutionality.

The PAS is an alcohol detection device. It samples the ambient air in an area and determines the presence or absence of alcohol in that sample. For the purposes of enforcing alcohol-impaired driving laws, the PAS should be used within 6-10 inches from a driver's mouth, preferably when the driver is speaking. The PAS immediately alerts police to the presence of alcohol in the sample. The PAS is distinguishable from preliminary breath test (PBT) devices and evidentiary devices by the sample it collects. The PBT and evidentiary tests require the subject to blow into a mouthpiece, providing a sample of unadulterated breath.

The PAS is more objective and reliable than an officer's nose. Field research at sobriety checkpoints shows that police commonly fail to detain about 50 percent of drivers whose subsequent PBT results are 0.10 percent. Use of the PAS significantly improves detection rates.

Although the PAS has been used since the 1980s, there are no reported cases analyzing the legal issues raised by the PAS under the Fourth Amendment. Because the PAS is non-intrusive and it does not extend the length of time a subject is detained either at a checkpoint or a traditional traffic stop, its use should easily be found to meet the reasonableness requirement for searches under the Fourth Amendment. However, it will be better if, before addressing the reasonableness of using the PAS, courts analyze the PAS to determine whether its use constitutes a search. If it does not, the Constitution does not limit use of the PAS during a legal stop.

The Fourth Amendment protects persons from unreasonable searches and seizures. A traffic stop is a seizure and must be based on reasonable grounds. Everything in this analysis assumes a legal stop. However, for the purposes of the PAS, the threshold question is whether its use constitutes a search under the Fourth Amendment. Not all investigations are searches. Those that invade a constitutionally protected area are searches. Courts ask three questions to determine if an area is protected.

First, does the person have an expectation of privacy that is reasonable under the circumstances? In this case, do we have an expectation of privacy in the air near our bodies? Second, is that expectation of privacy one society recognizes as valid? In other words, a bizarre or idiosyncratic claim to privacy, however heartfelt, will not be recognized. Third, has the person claiming a privacy interest actually kept the object private, or could that person in ordinary society maintain the privacy he claims? A negative response to any of the three questions results in a finding that there is no Fourth Amendment interest to be protected because collecting the information in question did not constitute a search under the Fourth Amendment.

Use of the PAS falls well within the plain sight doctrine. It teaches that observations an officer makes with his senses, from a vantage point from which he or she has a right to be, do not implicate the Fourth Amendment. In other words, in the traffic context, if the initial stop is legal, what is plainly revealed to an officer through the use of his sight or other senses, is not the product of a search. Other case law is highly relevant and leads to the same result. For example, under a line of cases that could be called appearance and demeanor cases, courts have held that we have no privacy interest in the way we look, or walk, or talk, or in our handwriting, because these are things we commonly reveal all the time in society, and in many cases, could not help but reveal.

Respiration and smelling are physical processes that we cannot prevent from occurring. Expired breath is necessarily a component of the air around the body of any living being. People in close proximity to any living being breathe and necessarily inhale a sample of air that may include expired breath. It follows that the sample an officer takes when he uses his unaided nose to detect alcohol is subject to the plain sight doctrine. Collecting it does not constitute a search. Collecting it using a PAS does not change the analysis.

The advantage of this analysis over a reasonableness analysis is that a finding that use of the PAS is not a search permits officers to use the PAS on all drivers legally stopped to determine if there is cause to suspect an alcohol violation.

For further information on the laboratory and field tests of PAS devices and for citation to legal authority on the issues described above, contact Michele Fields at the Insurance Institute.

PAS is the recognized leader for its expertise in the field of passive alcohol sensor technology. Our passive alcohol sensor designs are based on twenty-five years of research by independent and government traffic safety organizations.