The history of the alcohol breathalyzer is a sordid affair. From the secret sauce of proprietary source codes to the magic number of blood alcohol concentration, it’s primarily a victory of Mothers Against Drunk Driving using anecdotes of tragic deaths of children to sway a nation to believe in the syllogism: something must be done. And so it was, vilifying drunk driving as inchoate murder, at best, and putting a lot of otherwise law-abiding people in the docks, if not prison, along with all the consequences for them and their families.

Aside from criminal defense lawyers, no one cried for the drunk drivers. Even if they weren’t really drunk drivers, but no one cared enough to parse that nuance. When it comes to criminal law and anecdotal tragedies, we love to cherry pick between those we favor and those we don’t, even if it changes from time to time as the winds of feelings blow.

Want to know what’s wrong with the magic black box, with a BAC that fails miserably to take into account a wealth of detail that distinguishes a dangerous driver from a non-dangerous one, why we’ve demonized a huge segment of society that, but for kismet, would make it home fine and sleep it off unless they get nabbed and have their life ruined? No, of course not. Drunk drivers are bad people who threaten the lives of our children. And they do, but then, taking a scalpel to the problem would require that people thought, people cared, and a hammer is far easier to wield, so a hammer it is.

Now there’s marijuana to add to the problem, except it’s in its infancy so we know far less about it than alcohol and are far less prepared to address it. Therefore, it needs a hammer too.

Despite marijuana’s growing acceptance nationwide and its legality for recreational use in California, there is no consensus on how THC, its psychoactive ingredient, affects drivers or what levels constitute driving under the influence. That has left lawmakers, police and users grappling with a critical question: If you’re using marijuana, when is it safe to get behind the wheel?

An Oakland company believes it’s solved one piece of that puzzle. By mid-2020, Hound Laboratories plans to begin selling what it says is the world’s first dual alcohol-marijuana breath analyzer, which founder Dr. Mike Lynn says can test whether a user has ingested THC of any kind in the past two to three hours.

The weed black box is more humble than the Breathalyzer 5000. It doesn’t provide a number, so Mothers Against Weed Driving can ask their representatives to make it a felony to drive with more than .05% BWC. It’s just a binary machine, you either ingested THC in the past two or three hours or not.

How does it work? Ah, that’s likely proprietary, since you can’t sell the secret sauce if you give your competitors the recipe. But even if it does, what does it tell you? Weed affects different people differently (like alcohol does, but we’re way past that now). Does some get you stoned while other chemical variants have other effects? How high is high? How high must one be to be too impaired to drive safely? Does that apply to every driver the same way, as a first time user might have a very different impact than a daily user?

We don’t know. Dr. Mike Lynn doesn’t know. The cops don’t know, and surely the legislators, who might be inclined to write laws creating crimes in reaction to the tragedy that will certainly happen some day, don’t know.

Law enforcement agencies already are testing the breath analyzers and competing roadside devices like oral swab tests. But experts say there’s a long way to go before any of the emerging technology can or should be used as evidence in a courtroom.

There’s an interesting distinction to be found in here that might be missed by the unwary. Admission into evidence in court is one thing, and aspirationally requires some tiny pretense of actual scientific fact, although that’s mostly respected in the breach and lengthy National Academies of Science reports that are swiftly shelved. But what’s needed for court isn’t the same as what’s needed for a stop, an arrest, and the joy of sitting in a jail cell while waiting to see a judge, perhaps even a lawyer according to where you happen to be.

It may be a while before Weed Analyzers are admissible as evidence at trial, but they may well find their way into the hands of cops on the road long before any of these plethora of problems are answered. And as the saying goes, you can beat the rap, but you can’t beat the ride. Ironic, right?

Seems unfair, irrational, counterintuitive, to use a black box that tells a cop nothing of substantive utility as a basis for probable cause for arrest? Have you forgotten about the magic puppies of dog sniffs, with a probability no different than a coin toss of detecting drugs? Or drug field testing, which uses tests scientifically known to be very accurate as a preclusive measure, that no drugs are present, but has false positives off the chart for inclusive tests, that the substance in question is drugs? Glazed donuts, anyone?

Lynn stressed that his mission is one of fairness. He says he has a more equitable approach for both police and employers than to test with blood and urine, where chemical compounds found in cannabis known as cannabinoids are detectable long after a person is high.

“The challenge I knew from a law-enforcement standpoint is that … all that kind of testing that is available is totally unable to differentiate between someone who used five days ago — and is clearly not impaired — versus somebody who used an hour ago,” he said.

Dr. Lynn is right that it could be worse, that the ability to test for historic use of THC would certainly suck in people for whom weed was nothing but a fond memory. But having a better idea than a really bad idea doesn’t make it a good idea.

While Lynn’s test, assuming it works, would at least distinguish the person who just got high from the person who partied a week ago, how does it distinguish the person who isn’t one toke over the line from the one who just bogarted that joint? It can’t, so both will get hammered, because that’s the only tool available.

H/T Elizabeth Joh