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Comment by chadash | Hacker News Reader

> What’s keeping you in check?

It's going to be fairly easy to test this. You take one group of people who haven't smoked in the last few hours and you test them. Make sure it doesn't go off. You take another group who have smoked (I'm sure plenty of college students would be happy to sign up for this trial) and you test them, make sure it does go off. It's pretty simple. It's a machine with an empirical number, so you don't even have to do this double blind.

And if it doesn't give good results? It won't hold up in court. Every lawyer defending someone with a positive result (whether false positive or true positive) will argue that the device isn't accurate and the case gets tossed (or even the ability to use these as evidence). If it doesn't hold up in court, police really won't have much incentive to use these anyway.

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Even alcohol breathalyzers are regularly miscalibrated or defective and found to produce false positives. Legal pressure from manufacturers keeps this quiet.

https://www.zdnet.com/article/draeger-breathalyzer-breath-te...

That is why many states follow a positive breathalyzer test with a blood test. In my state, you can refuse them both, but you lose your license temporarily for doing so. I think that's fair. I understand some are skeptical about giving blood to the police, but if you can't prove you're not drunk or high after a positive reading on a less accurate device, then you aren't allowed on the road. The risk is too great for everyone else.

In Texas, you receive a mandatory suspension for refusing just a breathalyzer, even if you are found to not be over the legal limit, or are never convicted of a DWI. Blood tests are then often obtained via warrant (and it's typical to have a judge "on call" to sign and fax those orders on demand)

That's utterly disgusting that the state can invade your body and take blood out with a warrant.

You agree to these things when getting a license. It's like the EULA we never read.

I personally think it's utterly disgusting that people are allowed to operate what are essentially giant weapons in public with extremely minimal testing or training, and with minimal limits on alcohol usage. I think it's totally reasonable to ask people to give up some of the rights they'd normally have, when those people want to operate heavy machinery in public.

My understanding is that GA pilots are not allowed to fly within 8 hours of consuming any alcohol (my understanding is that most commercial outfits have more stringent limits) - I personally think this makes a lot of sense for operating a motor vehicle, too.

It takes between 1 - 3 hours for a single mixed drink or pint of beer to be metabolized.

As a starting point I think you will agree that someone who has a BAC of zero ought to be able to drive.

The majority of drunk driving accidents are the result of people that are plowed. More disturbing by far those who ARE caught and jailed have driven hundreds of thousands of miles drunk as a skunk before actually getting taken off the road.

As BAC decreases accident rates decline towards normalcy at around 0.06 its difficult to distinguish the accident rate of those who have consumed and those who have not.

People at that point neither walk nor drive funny and are very unlikely to be discovered unless you stop and test everyone or you happen to be black or Hispanic.

Instead of tightening already reasonable standards to ridiculous levels we would save vastly more lives by actually enforcing the laws we have effectively.

>As a starting point I think you will agree that someone who has a BAC of zero ought to be able to drive.

Not if they are tired or hungover. I mean, I don't think people should drive when they are tired for other reasons, either. It's a dangerous thing, and something you should only do when you are at your best.

Alcohol is just an easy target (and an important target) because it both degrades your actual ability, while at the same time, increasing your opinion of your ability. Because of that second effect, it's especially difficult to tell when you have had too much to drive... because one of the common side effects of alcohol is an increase in confidence.

It should be difficult to drive, and it should be easy to lose the ability to drive.

>Instead of tightening already reasonable standards to ridiculous levels we would save vastly more lives by actually enforcing the laws we have effectively.

eh, we already have rules against driving tired. they just lack an objective test.

I think that if you think you can operate a motor vehicle or a gun in public at 0.06, you are not being nearly careful enough. (And I suspect the additional confidence that alcohol gives you might actually contribute much to accident rates. I know I certainly feel more confident one drink in, and confidence is deadly when you are operating weapons or heavy machinery around other people.)

If the device is wildly inaccurate why would you be obliged to prove your innocence barring other evidence of impairment.

It points very strongly toward intoxication. There is just enough false positives that they are required by the state to also take a blood test.

It's a confirmation, and when you're about to sentence someone on the spot with what is often a life changing, multi year disqualification from driving, the courts require the police to be absolutely sure.

You're usually free to refuse the blood test, but the DMV is also free to revoke your license arbitarily.

It is not that simple. Within the control group of non-smokers you need people who smoked yesterday or 12 hours before to determine if the testing is successful.

But even that is too simplist. You need to activity give a specific dose to a group with similiar profiles. You need to test with different profile groups.

Remember we are testing currently high not has been high.

The basic functionality of a breathalyzer is to take a given volume of an exhale and measure the concentration of a given particle as an indicator of intoxication. So long as an individual's results are greater than or equal to 0.08 then it becomes an unacceptable risk and they are considered intoxicated. If this process is going to test in a similar way, there is no need to test specific doses or profiles because the concentration isn't variable, it's a static amount. With alcohol, we don't consider weight, or what they had to drink, or how long they've drank so why should this be any different? All that needs to be defined is what the law considers a concentration which should represent a level where the risk reaches an unacceptable percentage.

I think maybe you misunderstood @wolco's point? I think what they are saying is that, for example, you might do all of your testing on college age males and find that it doesn't give any false positives for people who smoked yesterday but not today. But you still need to test it on 60 year old women to make sure it doesn't give false positives there. In other words, you need to test it for varying lengths of time and also to make sure that it has consistently acceptable results by race, sex, weight, age, etc.

If that is indeed what they're saying, my point still stands. The blood alcohol limit has no variations for age, sex, gender, race, weight, time since last usage, or any other factor. It just goes by concentration. My point still stands. What the law considers the concentration which indicates intoxication is a metric based on what is considered an acceptable level of risk.

Additionally you need to test it doesn't trigger a positive when someone had a cinnamon flavored mint before. Or a citrus one. Or ate a mushroom sandwich. Or has diabetes..etc etc

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