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What’s the Difference Between a Preliminary Alcohol Screening Device, the Blood Test and the Breath Test in a DUI?

These are all tests that are designed to try to detect whether somebody’s blood alcohol level is a .08 or greater.  First, when they stop somebody at a traffic scene, the police,  after they talk to the person, ask them a bunch of questions and maybe even perform a field sobriety test.

Just so they don’t waste a trip into the police station, a lot of times they will have the person blow into the Preliminary Alcohol Screening Device or PAS.  Basically, it’s a small device that they carry along with them in their police vehicles.  Its accuracy is probably the worst of the three tests, but it certainly does measure alcohol.

They weren’t usually allowed to get in what the result was years ago.  I’ve been doing this for 25 years, but now they can actually usually get that result in.  The defense will try to block it, but depending on the circumstances of the case, the judge may or may not actually let that PAS result.

So, that’s something that’s usually going to be done at the scene of the accident.  It’s one of the least accurate of the three tests.

Breath Test in DUI Cases

The breath test is the next test they will usually try to administer.  That’s usually in Los Angeles County done at the police station where they have you blow into a tube.  It’s attached to a machine that registers your blood alcohol.Preliminary Alcohol Screening Device in California DUI Cases

They usually like to get at least two results so that their expert can try to show at a trial that your blood alcohol level was a .08 or greater and hence, get you for a DUI.  This machine is called the Intoxilyzer 3000.

It’s a machine that does have issues with its accuracy.  In general, most experts — even the prosecutor’s experts — will probably say it’s got an error rate of a .02.  So, if you blew a .08 according to the machine, you could arguably be a .06.

That’s why a lot of times in Los Angeles County the prosecutors will give something less than a DUI to resolve a case where the person blew a .08.  Of the three tests, this is probably middle of the road as far as accuracy, but certainly something the prosecutors use every day in convicting people for DUI cases.

These machines have to be calibrated.  Sometimes there’s problems with them.  That’s another area to look at, especially if you suspect the machine may have inaccurately registered your blood alcohol level.

That’s why I always ask my clients whether or not they’ve had anything to drink; how much they’ve had to drink.  We find out what their body weight is; how much they’ve had to eat and a host of other factors are going to be evaluated in making a determination whether or not they’ve got the right blood alcohol level.

I’ve been doing it for 25 years, so usually once I can plug in where you’re at, I can get a pretty good idea of whether there’s some sort of a problem with either of the two breath tests.

Blood Test in DUI Cases

Lastly, there’s the blood test.  That’s the most accurate test and usually what we will do if it’s a close one — for example, the person blew a .08, .09, we may do what’s called a blood split where we would test the blood ourselves with our own expert to see if the police got it right.

This is obviously good to do especially in a close case or if you suspect some sort of contamination in the blood, which is another way to up-end the prosecutor’s key evidence to prove that the person was a .08 or greater.

So, these three tests are used independently.  Sometimes they’re all used together.  It depends on how successful the police are in getting somebody’s blood or breath result and obviously, with the implied consent law in California, if you don’t give your blood or breath, then you’re going to automatically be presumed to be DUI and you’ll also lose your license for a year with no restriction.

So, they’ve got it set-up pretty well and these three tests are the main evidence that they use to prove DUI cases in Los Angeles county.

So, if they use these tests on you — either one of them or a combination of them — obviously you’re going to want to sit down with somebody like me who can evaluate whether or not they’re accurate and what you should do in your DUI case moving forward.

Hedding Law Firm is a criminal defense law firm located in the San Fernando Valley area of Los Angeles County at 16000 Ventura Blvd #1208 Encino, CA 91436. We are also located at 633 West Fifth Street Los Angeles, CA 90071. Contact us for a free case evaluation at (213) 542-0963.

Downtown Los Angeles Metro – DUI Courthouse

We have successfully handled thousands of DUI cases in this courthouse over our many years of practice. Division 60 is the arraignment court in downtown Los Angeles for DUI related cases. We are frequently in this particular court dealing with the prosecutors and the judge regarding DUI cases. Our experience related to DUI cases in the Metro Courthouse has been invaluable and extremely effective in successfully resolving DUI cases in Los Angeles for our clients.

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Ronald D. Hedding

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