Breathalyzers will tell you what's up right on the spot, unless you've come across some that require the cops to collect a jar of your breath for processing at some remote discrete location?
Breathalyzers are easily tampered with by police to provide false readings. One case of this in New Jersey could have potentially thrown out 20,000 DWI cases. But breathalyzer results in cases today are not thrown out after pointing this out.
It's irrelevant that breathalyzers in New Jersey were tampered with. You would need to show evidence that the breathalyzer in your specific case was tampered with. It's a basic rule of evidence...
In this case, a few breathalyzers were not calibrated correctly, but the officer responsible for testing them claimed to have done so. Now every device and calibration procedure is called into question, as their results may not be as verifiably precise as required by law. The device itself is not claimed to have been tampered with.
The prosecution will present calibration logs and security tampering prevention information to show that the device was independently verified as working correctly and demonstrably unchanged from that inspection date. A lot of people's careers rely on those records being correct, up to including a perjury charge if they're falsified.
IANAL. I had this talk with a lawyer friend a few weeks ago. I thought there was a way to show the design of the device is faulty - for example a speed gun at sunset reports inaccurate times. But it's a very high standard to get a court to allow that.
That why where I live if you trigger the drink driving limit on a breathalyzer you're driven to the station where a medical professional will take your blood and send it to an independent lab.
