
Developing a viable cannabis breathalyzer - newman8r
https://www.npr.org/2018/08/04/634992695/the-pot-breathalyzer-is-here-maybe
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ohiovr
I would like to know how this works. THC is an oil or resin. For it to appear
in your breath it has to be a vapor unless it is rolling out of your mouth as
smoke. What is the vapor pressure of THC?

~~~
bribroder
Here's an interesting tidbit:

The tricky thing about THC, however, is that it is a large and complex
molecule unlike ethanol, the main compound in alcohol, which is relatively
small and simple. According to Tom Bruno, a NIST research chemist and co-
author of the new paper, the vapor pressure of the THC compound is “very, very
low,” which makes it difficult to measure.

Bruno, along with fellow NIST researcher and lead author Tara Lovestead, found
a way to skirt around this issue by measuring THC vapor pressure with a vapor-
capturing technique called PLOT-cryo. It works by trapping vapors in a solid
substance that coats the inside of a small tube. Because the tube is so small,
Bruno said, the process is very efficient.

“You don’t have to collect a lot to get an analyzable result,” he remarked.

The PLOT-cryo device works like a very sensitive nose. It can sniff out
different compounds from the air, and has been previously used to identify
explosives as well as decaying flesh.

[https://www.seeker.com/health/new-thc-finding-paves-the-
way-...](https://www.seeker.com/health/new-thc-finding-paves-the-way-toward-
an-effective-marijuana-breathalyzer)

~~~
ohiovr
Thank you that was interesting.

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hirundo
Why use less reliable proxies like breathalizers to gauge impairment when we
now have the technology to measure it far more directly: convert traffic cop
cars into mobile virtual reality driving simulators.

Put a gaming laptop in the trunk, and the DWI suspect behind the wheel with a
VR headset on and let them drive through a couple of minutes of reasonably
challenging simulated traffic. Let software come up with an objective score
and store the simulated session as evidence if they fail.

Not only does this more directly measure impairment, it catches any cause of
it, not just a particular substance. Virtual driving impairment will correlate
with real driving impairment far better than parts per million of a molecule
in the bloodstream.

~~~
pmichaud
It's an interesting idea, but the critical issue with it is that it's not
illegal to be bad at driving. That could change, but that's how it is now.

~~~
mjfl
If someone drives as if they are drunk, all the time, then I don't think they
should have a license as they are clearly a danger to public health. On a
similar note, the driving test for a license could include a run in the
simulator to both test driving skills and establish a baseline for the test.
Then the impairment could be measured as relative to that baseline.

I think it's a good idea.

~~~
bdcravens
> If someone drives as if they are drunk, all the time

This doesn't test "all the time". It only tests at one point in time.

States have entire sets of due process for removing someone's license due to
medical reasons, etc. It's not on the spot based on a video game running from
a laptop in an officer's trunk.

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scarface74
It couldn’t be any worse than “specially trained officers” who are able to
detect whether someone is high by thier mannerisms and arrest people who
aren’t using anything.

[https://www.11alive.com/article/news/investigations/the-
drug...](https://www.11alive.com/article/news/investigations/the-drug-
whisperer-drivers-arrested-while-stone-cold-sober/85-437061710)

~~~
NikolaNovak
That article is completely terrifying.

* I am much too much of a control freak to ever ever try drugs; no moral issue, just not for me.

* I have a drink of something on social occasion maybe once or twice a year, maybe not. Never got behind the wheel with even a sip of alcohol that day, let alone a glass, let alone anything approaching legal limit.

But I'm a klutz and I'm an introvert and I get nervous easily and I have _NO_
idea what kind of "signs" my body would display in stressful situation with a
police officer at night (my body an my brain have an uneasy working
relationship - we mostly put up with each other:).

It is very literally my nightmare scenario to be accused by a police officer
of intoxication where none exists. As much as I 100% support them, I'm
probably more afraid of roadside checks than an actually inebriated person.

~~~
rocky12
I was charged with a DWI a year ago. The case is still going through the court
system.

I was pulled over for speeding, going 36 in 35. Yes I am serious, one mile
over. But this wasn't surprising to me, I am a young Hispanic man so this is a
normal occurrence for me.

First thing the officer said was "boy you look nervous". As most adults pulled
over by police feel. I handed my license and insurance over. The license had
my old address the insurance had my most recent. He asked? "Is this your
address", "yes", "why is the address different?", "because I moved a couple of
months ago and have not had time to drop by the DMV", "Step out of the car
sir"

I refused the field sobriety test but offered a breathalyzer. I blew a .034,
that's less than half the legal limit.

He asked more questions, I answered but was short and untalkative.

He ended up arresting me. I asked him, why if I blew half the legal. He gave
me three reasons. One; I was speeding and that I must be intoxicated to not
notice the speed signs, two; I was uncooperative and nervous and that's a sign
of drug or alcohol use, and lastly I forgot my address so I was obviously
impaired.

The latest offer from the prosecutor was moving my charge down to reckless
driving with 1 year of probation. My lawyer says I can probably get it
dismissed.

It has been the worst experience of my life. Thank god I have enough money to
hire one of the best lawyers in town, for $7k btw.

~~~
IAmGraydon
I must be missing something here. What are you actually charged with? DUI? How
can that stand in court at all if the breathalyzer obviously proves you were
under the limit?

~~~
sithadmin
In most US states, the 'legal limit' as detected with a breathalyzer is just a
threshold that results in automatically being charged with a DUI/DWI if you
exceed it. Blowing under the threshold doesn't provide you any kind of legal
protection against being charged with a DUI/DWI.

~~~
snvzz
So, in short, you should never blow, as that's never going to help you in any
way?

~~~
evil-olive
In most states, refusing a breathalyzer test can cause suspension of your
license, even if you are completely sober:

[https://dui.findlaw.com/dui-arrests/can-i-refuse-a-
breathaly...](https://dui.findlaw.com/dui-arrests/can-i-refuse-a-breathalyzer-
test-.html)

Sadly, as with many things in our criminal justice system, the answer ends up
being "hope that you're not prosecuted by mistake, and that you have enough
money for a lawyer if you are".

