Where Breath Testing Goes Wrong and Why It Matters

A number printed off a machine lands differently than an officer's opinion. It looks like a measurement. Measurements feel like facts.

That impression does a lot of work in these cases. It's the reason most people quit before anyone has bothered to ask how the number got there in the first place.

A DUI lawyer in Salinas working on a case with a breath result wants to know three things right away: how the machine was maintained, who ran it, and what was happening twenty minutes before you were tested. This doesn’t mean the technology is obsolete. It is simply a process with rules attached, and processes leave paperwork.

The Machine Does Not Measure Your Blood at All

The instrument reads your breath and then converts that into an estimated blood alcohol number using a ratio. The ratio comes from population averages. Real people land above and below it, sometimes by a lot, depending on their physiology and what's going on that night.

So what prints out is an estimate produced by a formula. It rests on assumptions, and assumptions can be argued about.

Alcohol Left in the Mouth Skews Everything

This one's been known for decades, and it still comes up constantly.

If alcohol is sitting in your mouth rather than coming up from your lungs, the reading can land far above where you actually are. It doesn't take much:

• A burp or a hiccup at the wrong moment
• Reflux, which plenty of people have and never think about
• Bridges, dentures, or dental work that holds fluid
• Breath spray, mouthwash, some cough medicines
• A drink finished right before you got in the car

That's the whole reason there's supposed to be an observation period first, with the operator watching to make sure nothing goes in your mouth, and nothing comes back up.

What happens in the real world is that the period gets cut short, or interrupted, or the officer spends it filling out forms with his back turned. Whether it was done properly is a documented question, and the documents don't always help the state.

Paper Trail Associated With Maintenance and Calibration

Evidentiary machines have to be checked for accuracy on a schedule and fixed when they drift.

This must be noted. Paper trail includes accuracy logs, repair records, solution batches, and operator certifications. Your lawyer can ask for them and spot gaps like a failed check or a device that went in for service right after your test with nobody mentioning why.

There's nothing exotic about this. It's filing cabinet work, and it's the first thing to go after.

Physiology and Technique Both Affect the Result

A handful of things can move a reading without anyone drinking more.

People in ketosis — diabetics, anyone on a serious low-carb diet — produce compounds some instruments don't sort out well. Body temperature matters. So does how you blow, since a long hard breath and a shallow one don't sample the same air.

Operators are trained to collect samples a specific way and to get two readings that agree within a set range. Whether that happened, and what both numbers were, is worth knowing before anyone accepts the result.

Roadside Devices Are Not the Same Thing

People mix these up all the time.

The handheld the officer carries and the machine back at the station are different devices, with different reliability and, in many places, different legal standing. A roadside number might be good for one purpose and not another.

If you blew twice, once at the scene and once later, those are two separate pieces of evidence, and they don't rise or fall together.

The Gap Between Driving and Testing Matters

Alcohol keeps absorbing for a while after you drink it. Someone tested an hour after driving can come out higher than they actually were behind the wheel, because the level was still climbing the whole time.

How much that matters depends on when the last drink was and how long the stop, the ride, and the booking took. It's one of the reasons the timeline of the whole night gets pulled apart carefully.

Final Thought

None of this means a breath result is garbage. Plenty of them are accurate, and plenty of cases turn out to be exactly what they look like.

What it means is that the number came out of a device, run by a person, under conditions that were supposed to meet certain requirements. Each one generated a record, and the records can be pulled.

Most people never ask. They see a number over the limit and figure it's finished, without anyone checking whether the machine passed its last accuracy test or whether that observation period was actually observed.

Pulling those records is ordinary work in one of these cases. Worth doing before you decide what the number is really worth.