Can a Police Officer Validly Detect Whether or Not You Have Been Smoking Marijuana?

marijuana-leafDriving under the influence of marijuana is a serious crime. Getting caught can mean penalties like jail time, fines and license suspension.


We’ve been asked many times before about the possibility of a cop smelling marijuana on you. Below are some considerations in view of this:

  1. Just because someone smells of smoke doesn’t necessarily mean that he or she has smoked. The odor from your clothes might have been caused by someone smoking next to you. Similarly, just because your clothes smell like marijuana doesn’t necessarily mean that you have marijuana on you or have been smoking it. You may have been sitting near others who were smoking it.
  2. Smelling a substance does not count as primary or direct evidence of possession or use. It’s a non-standardized, non-scientific and completely subjective approach.
  3. There are many substances that can produce similar smells. So, to say that something smells like “smells like pot” is quite an inaccurate means of concluding that it is so.
  4. Each person’s sense of smell is likely to be at a different level. This makes the idea of using a smell as confirmation of marijuana usage very misleading.
  5. Bias may result due to an officer having a pre-conceived notion of someone smoking marijuana; and if there is a strong smell detected, that gives the officer his confirmation, whether that’s right or wrong.
  6. There are also perfumes that smell similar to marijuana. What if a person is caught when he or she is wearing something like Kush Perfume that smells fairly similar to marijuana?

The idea that that something “smells like marijuana” reports a completely unverifiable subjective opinion. Smell is also massively open to confirmation bias, which makes it a completely unreliable tool for drug testing.

If you have been falsely accused of a marijuana violation, please call 1-866-MCSHANE to find out what we can do about it.

Justin McShane

PA DUI attorney Justin J. McShane is the President/CEO of The McShane Firm, LLC - Pennsylvania's top criminal law and DUI law firm. He is the highest rated DUI attorney in PA as rated by Justin McShane is a double Board certified attorney. He is the first and so far the only Pennsylvania attorney to achieve American Bar Association recognized board certification in DUI defense from the National College for DUI Defense, Inc. He is also a Board Certified Criminal Trial Advocate by the National Board of Trial Advocacy, a Pennsylvania Supreme Court Approved Agency.

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