Philadelphia, PA: Marijuana’s odor is seldom discernible enough to justify probable cause by law enforcement officers, according to empirical data published in the journal Law and Human Behavior.
“Although law enforcement officials routinely rely solely on the sense of smell to justify probable cause when entering vehicles and dwellings to search for illicit drugs, the accuracy of their perception in this regard has rarely been questioned and, to our knowledge, never tested,” authors at the Smell and Taste Center at the University of Pennsylvania School of Medicine wrote. Researchers evaluated data from two empirical studies based upon actual legal cases in which police relied on the odor of marijuana as probable cause for a search. In the first, they simulated a situation in which, during a routine traffic stop, the odor of packaged marijuana located in the trunk of an automobile was said to be detected through the driver’s window. In the second, researchers investigated a report that marijuana’s odor was discernible from a considerable distance from the chimney effluence of diesel exhaust emanating from an illicit grow room.
Six of the nine participants in the first trial were unable to detect the odor of marijuana. In the second trial, none of the participants could reliably detect the marijuana odor embedded in the diesel fumes.
“Our findings suggest that the odor of marijuana was not reliably discernible by persons with an excellent sense of smell in either case,” authors concluded. They further noted that odors emanating from immature female plants are much less intense on average than those of mature females, and that no marijuana-like odor could be discerned in most immature plants.
“The present findings throw into question, in two specific instances, the validity of observations made by law enforcement officers using the sense of smell to discern the presence of marijuana,” authors wrote. “Although these instances reflect a very small set of studies with very specific constraints, they do suggest that a blanket acceptance of testimony based upon reported detection of odors for probable cause is questionable and that empirical data to support or refute such testimony in specific cases is sorely needed.”
For more information, please contact Keith Stroup, NORML Executive Director, at (202) 483-5500. Full text of the study, “Marijuana Odor Perception: Studies Modeled From Probable Cause Cases,” appears is the April issue of Law and Human Behaviors. It is available online at:
http://www.kluweronline.com/article.asp?PIPS=484203