content: This sort of tech is also not anywhere near reliable as breathalyzers, even assuming they're actually detecting THC levels on the breath.  With THC, the body develops a tolerance, so someone at a certain blood percentage may or may not be impaired based on their tolerance.  This is not true with alcohol, so it's easy to set a baseline blood percentage and call it impaired for alcohol, but is not anywhere near as reliable with THC.  The fact that this article didn't mention that is not indicative of good, unbiased science.