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Video: Driving-stoned blood tests all over the map in CBS4 report

After the passage of a driving-under-the-influence-of-drugs bill, we wondered if Westword medical marijuana critic William Breathes would ever be able to drive legally again, since he'd registered nearly triple the proposed limit while sober during a 2011 test.

Tonight at 10 p.m., CBS4 dives into the drugged driving debate -- and its tests of various subjects showed wide variations, both when users were stoned and sober.

See a preview video, a clip of a previous TV report on the subject and more below.

As we've reported, driving while stoned has long been illegal under Colorado law. But unlike in the case of alcohol, there's no number at which a marijuana-using driver was considered to be officially impaired -- and cannabis activists saw that as a good thing, since the science on the subject is infinitely less certain than it is in the case of booze. Nonetheless, the medical marijuana industry boom caused assorted legislators to believe one was needed anyhow.

Similar pressure's been building in Washington, which joined Colorado this past November in passing a law that allows adults 21 and over in the state to use and possess small amounts of marijuana. Against this backdrop, Seattle's KIRO-TV produced a report this past February that put stoned drivers through their paces in a series of road tests -- and most of them failed badly, by either going far too slow or swerving into cones on a simulated driving course. Here's that package:

Reports like this one provided momentum for the latest THC driving bill, which shared most elements with proposals that fell short in 2011 and 2012, but differed in one significant respect.

All three pieces of legislation established THC intoxication at five nanograms per milliliter of blood, but the first two made the standard per se -- meaning that a test registering five nanograms or more would be seen as irrefutable proof of intoxication. In contrast, the most recent version subbed in the phrase "permissible inference," thereby allowing people who register at five nanograms or above to present other evidence in court to prove that they weren't actually impaired, rather than being considered guilty as a result of the test reading.

Plenty of people still objected to the bill, including marijuana attorney Rob Corry. But it was approved by the Colorado legislature anyhow, and Governor John Hickenlooper is expected to sign it soon.

But given that marijuana reacts differently in each user, how accurately does the five nanogram rule establish impairment? Although Mark Ackerman, who produced the Rick Sallinger-starring segment, concedes that the CBS4 piece on stoned driving doesn't qualify as a scientific study, he feels it raises as many questions as it answers.

Continue for more about the CBS4 report about stoned driving, including photos and a video.

An image from the CBS4 report.
An image from the CBS4 report.

According to Ackerman, the station worked with local dispensaries to identify three individuals willing to take part in the test. Each one of the trio wound up having his or her blood tested four separate times -- once prior to the first driving test, conducted at a Master Drive range, then three additional times after marijuana consumption.

The participants are all regular marijuana users, and each suspected that he or she would register over five nanograms when sober as a result. (They abstained from marijuana use on the day in question until the test got underway, at around 11 a.m.) Yet two of the three were under the soon-to-be legal standard: One registered at 1.4 nanograms, another at 1.8 nanograms.

The third, however, checked in at 11.2 nanograms, more than double the limit, even though she hadn't smoked since the night before.

During the first test, which was intended to establish a baseline, the three participants did fairly well on a challenging course with which a CBS4 employee who navigated it as a control subject also had difficulties. But that employee did successively better during each subsequent drive, while the skills of the other three tended to deteriorate.

Granted, they smoked before the additional tests. Before the second drive, Ackerman says they were instructed to use cannabis until they could feel it -- a point that might be equated to someone who knows when to stop drinking alcohol in order not to exceed the .08 blood-alcohol-content mark for legal intoxication. But all the marijuana users blew past five nanograms.

"They were way over," Ackerman says, adding, "I think there's a decent awareness of where people's personal .08 would be, but as far as pot users, I don't think they have any idea where five nanograms is."

Another screen shot from the report.
Another screen shot from the report.

These specific results, and those of the tests that followed, will be shared on the CBS4 website once the 10 p.m. offering airs. But from Ackerman's perspective, "it's too soon to tell" whether the five nanogram limit will turn out to be a useful way of determining marijuana intoxication, or if innocent people will wind up being convicted.

He notes that in the case of two participants, who stopped smoking after reaching what they considered their "high point," their blood THC "plateaued after test two and rapidly came down. And who knows what that means as far as the real world, when a police officer pulls someone over. For our test, we waited for fifteen minutes to let the marijuana set in, but it might take a lot longer during a traffic stop for a police officer to actually get a blood test done. Who knows where five nanograms would come into play with that...."

Here's a preview of the CBS4 report:

More from our Marijuana archive circa February 2013: "Driving-while-stoned videos help fuel momentum of THC driving bill."