DUI and the Presumption of Guilt

Posted by Lawrence Taylor on May 22nd, 2007

In most countries of the world, an accusation by the State forces the accused to prove himself innocent. In the United States, however, the presumption of innocence has always been a fundamental part of our rights as a free people.

This basic protection against the power of the government has been recognized as flowing from the 5th, 6th and 14th Amendments to our Constitution. As the United States Supreme Court has said, “The principle that there is a presumption of innocence in favor of the accused is the undoubted law, axiomatic and elementary, and its enforcement lies at the foundation of the administration of our criminal law.” Coffin v. U.S., 156 U.S. 432 (1895).

So what happened to this presumption of innocence in a drunk driving case? Is this yet another example of “The DUI Exception to the Constitution“?

Let’s take a look at how our DUI laws have slowly eroded this fundamental right….

Assume that you’ve been arrested for drunk driving, and a breathalyzer gives a reading of .09% blood-alcohol concentration (BAC). You will probably be charged with two crimes: (1) driving under the influence of alcohol, and (2) driving with over .08% BAC.

Let’s look at the .08% charge first. The .08% offense depends entirely upon the results of the breath machine (often called a “Breathalyzer”, although there are many manufacturers, makes and models). These machines are notorously inaccurate and unreliable for any number of reasons. But a funny thing happens when your attorney tries to bring out those reasons for the jury.

He tries to point out, for example, that the breathalyzer computes the results by presuming that the defendant has a partition ratio of 2100:1 (the ratio of alcohol in the breath to the alcohol in the blood) — but that this is only an average: in fact, the defendant’s ratio is much lower, so the .09% reading should actually be .07%. However, the judge stops him: the law presumes that all men are average — even if they are not.

The Supreme Court of California has specifically ruled that such scientific truth is irrelevant. In People v. Bransford, 884 P.2d 70 (1994), that high Court justified its ruling in a rather frank — and amazing — justification:


It (.08%) will increase the likelihood of convicting such a driver, because the prosecution need not prove actual impairment…Adjudication of such criminal charges will also require fewer legal resources, because fewer legal issues will arise. And individuals prosecuted under such a statute will be less likely to contest the charges.


In other words, ignoring scientific facts makes it easier — and cheaper — to convict.

What about the officer who gave the breath test? Surely, we can question his experience and the way he administered the breath test. And this raises a prosecutorial favorite: the “Official Duty Presumption”. The California Evidence Code (sec. 664) puts it very simply: It is presumed that official duty has been regularly performed. Period. That’s it: Since it was the officer’s official duty to give the test, the law presumes he did it correctly — and the burden is on the defendant to prove he didn’t.

Interesting twist on the presumption of innocence, huh? Well, so much for the .08% charge. At least the defendant is presumed innocent of the DUI charge, right?

Wrong. The laws of most states create a presumption of guilt: if the Breathalyzer reads .08% BAC or higher, the jury will be instructed that the defendant is legally presumed to be under the influence of alcohol. That’s right: the defendant is presumed guilty. As with the others, this is called a “rebuttable presumption” — that is, the defendant can try to rebut this presumption with other evidence. Put another way, he is presumed guilty and the burden is on him to prove his innocence. Just like in third world countries.

Ok, but the law says it’s illegal to have .08% BAC when driving — not when tested an hour later at the police station. If, for example, a person has a drink or two before driving, the alcohol will not be absorbed into the system for an hour or so: it will not be in his system while driving, but will be reaching peak BAC levels when tested an hour later at the station. So how does the prosecution prove what the BAC was at the time of driving?

Easy: the law presumes the BAC is the same. Let’s take a look at California’s fairly typical law:


In any prosecution…it is a rebuttable presumption that the person had 0.08 percent or more, by weight, of alcohol in his or her blood at the time of driving the vehicle if the person had 0.08 percent or more, by weight, of alcohol in his or her breath at the time of the performance of a chemical test within thre hours of the driving.


Well, now, that’s really amazing. The Legislature simply passed a law against scientific truth. We can absolutely say, with scientific certainty, that the BAC will not be the same three hours after the test — and yet the law says it is.

So much for the “presumption of innocence” in a DUI case….

Share