Often I am asked by those anticipating an eventual DUI arrest, or just curious sorts, whether they should submit to a blood or breath test if stopped. First of all, if you are under 21, you don't have a choice. Those under 21 must submit to a breath test upon a police officer's mere suspicion of alcohol consumption. They don't even have to place you under arrest first. And, when they do - guess what?- you have to take one more test. That's easy. So, what about the rest of us? Well, it's more complicated. You do have to submit to ONE chemical test AFTER the point of arrest. Should you take blood or breath? Well, if you are detained longer than 20 minutes, chances are neither one is going to exonerate you. In other words, either one of them is probably going to damage your chance of escaping a criminal charge, and an arrest-related drivers license suspension. Regardless, you have to submit to ONE of these tests anyway. And I emphasize ONE, because taking both is generally not in your interest; less is more. Fair or unfair, the law says you must submit to ONE of these tests. It is what is known as the "implied consent law" (i.e., the law which states that by driving a motor vehicle in California, one has impliedly consented to submit to a chemical test). Your refusal to submit to a test will result in a lengthy suspension to your drivers license, and your refusal will be compelling evidence of consciousness of your own intoxication which, most likely, will be every bit as effective at persuading others of your guilt as would a number. What's more, they'll likely hold you down and take your blood anyway. So, refusing is just not pretty. Oh, and look forward to an enhancement on the charge for your refusal as well. So, the choice of tests is a lesser of evils choice in most circumstances. And, no, you don't have a right to talk to a lawyer before you decide. A blood test is a good choice to guard against the well-documented and alarming fallibility of breath machines and it does allow you the option of retesting the sample, at your own cost, in a laboratory of your choice. However, a blood test is generally a bad choice if you have any other intoxicants (besides alcohol) in your system. Recent use of most recreational drugs will show up should the government screen for it, as will recent use of many prescription medications. Pain killers and sleep aids are considered intoxicants because, in some cases, they can affect one's ability to drive a motor vehicle safely (particularly where they are combined with alcohol). Keep in mind that marijuana stays in your system for at least 30 days and, worse, you won't find two scientists on the planet to agree on how to measure, much less decide, what amount of the active ingredient of marijuana is too minimal to affect driving. So, simply put, if you smoke weed, blow.
Breath can be a good choice when you know you are drunk (i.e., you strongly suspect you are well over the legal limit). The amount your BAC may drop, if it will drop, on the way to the phlebotomist, is likely too small to make a meaningful difference in the case and, by choosing blood, you are giving the government less impeachable evidence of your guilt. In other words, the immediacy of the breath test (as they are often administered at the scene) will not likely hurt you if your BAC is very high.
Whatever you do, don't ask the police officer for advice. Police generally like the convenience (to them) of a breath test. But, importantly, don't expect the person who is trying their best to gather evidence convict you of the charge to give you good advice.