This really has to do with DUI cases and the police and prosecutors trying to figure out what a particular person's blood alcohol level was in relation to a DUI and there's a number of ways that they can test that.
Right now, the legal limit in California is a .08. So, if you're found to have a blood alcohol level of a .08 or greater, it's presumed that you cannot safely operate a motor vehicle and the prosecutors can get you for a DUI.
Breath Test to Determine BAC
So, the most common way to measure your blood alcohol level is to do a breath test. You would go into the police station and blow into a machine.
It's measuring what your alcohol level is. It's pretty accurate. The prosecutors are able to call experts in to be able to testify to the accuracy and the science behind using one of those breath tests at the station.
Also, there's a hand-held device that the police carry in their police cars and motorcycles in order to test the person's blood alcohol level.
This is called the preliminary alcohol screening device or PAS — a PAS device — and this is not as accurate as the test at the station, but it's still a form of measuring somebody's blood alcohol level.
It's used all of the time by the police. It really seems that the reason they use that is just another tool to be able to determine is somebody cannot safely operate a motor vehicle.
Also, if the person is well-under the legal limit that will save them time and effort for dragging them into the police station to do the breath test, only to see that the person is only half the legal limit and they can't charge them with anything. So, I think that's another reason they use that to measure blood alcohol level.
Blood Test to Determine BAC
Another test that make sense is to do a blood test. They take your blood and analyze it and they see what your blood alcohol level was at a particular time.
Assuming they can pinpoint the time that you were driving your motor vehicle, they'll have an expert if the case goes to trial be able to extrapolate backwards and say, about 10:00 p.m. the person was a .10.
This particular person would have been a .09 for example at 8:00 p.m. when they were driving the motor vehicle. That's a type of evidence that the prosecutors use to prove these DUI cases.
Blood evidence is known pretty commonly in the DUI community to be the most accurate test available.
There's also a urine test that used to be used to law enforcement but is not used as frequently anymore.
Usually they use a urine test to see if they can determine whether somebody has some sort of drugs in their system for purposes of a DUI or to be under the influence of drugs, but urine is definitely another way to determine whether or not somebody's blood alcohol level is a .08 or greater.
Blood Alcohol Content of .08 or Greater
So, this whole concept of blood alcohol has to do with DUI's and whether the police are able to show that a particular person had a blood alcohol content of .08 or greater.
If the person is real close to the legal limit, obviously what test is utilized to test them becomes important, and also experts can become important in trying to evaluate whether or not a particular person is a DUI.
The example I would give you is in a blood case, somebody can do what's called a blood split where blood is taken and the blood is analyzed by your own expert in order to determine whether or not you were a DUI and then if the case goes to trial you can call your own expert.
If they get a different reading than when the police got when they evaluated your blood, if that reading is more helpful to you, your expert can testify, I got a blood split.
I was able to test the blood and my reading is different and I don't believe that the person was in a position where they could not safely operate a motor vehicle and here's the reasons why.
That would be a way to challenge the prosecutor's evidence, that they're going to try to show that your blood alcohol level was a certain level and try to make the argument that you could not safely operate a motor vehicle.
So, blood alcohol evidence is very important. It's probably one of the biggest factors that is used and evaluated by juries in DUI cases, but it's not the only factor. In addition to your blood alcohol level, they're also going to look at how you were driving.
They're going to look at how you were walking around, how you did on the field sobriety tests.
The police have a number of different tests and are specifically trained in these DUI cases to try and evaluate on a bunch of different fronts whether somebody could not safely operate a motor vehicle and obviously, it would be up to your defense attorney to challenge this evidence if you decide to take your case to trial.