Arizona DUI Defense Blog : by Lawrence Koplow, Scottsdale & Phoenix DUI Lawyer & Attorney | Koplow Law Firm

The truth of the matter is we don’t really know. Most labs in the Phoenix Arizona area claim to be accurate within 5%. That means if your blood result came back at .08, then the true result can be anywhere from 5% lower or 5% higher.

Other scientific organizations claim 5% is not a realistic range of accuracy. For example, the American Academy of Forensic Sciences claims that the accepted range of accuracy is 10% higher or lower.

After interviewing toxicologists over 100 times, doing a substantial number of DUI trials with blood results at issue, I am convinced that the accuracy is totally dependent on the procedures used by the lab, and most labs overstate their accuracy.

To support my conclusion, I need to explain how blood testing with a gas chromatograph works. At its most basic level, gas chromatography simply compares known alcohol concentrations to unknown blood samples. A blood tester does not inherently know what a blood alcohol concentration (BAC) is. You must calibrate it every time you do a test. You teach the machine what a .08 is by putting known alcohol concentrations into it, and essentially build a ruler.

Most labs in the Phoenix area put four known alcohol concentrations into the blood tester to build their ruler. These known concentrations are called calibrators. It is important to remember these calibrators are water based. That is, they are known alcohol concentrations in water. See the graphic below for an illustration.

As you can see in the example, there are four points on the ruler. The blood tester simply connects the dots on the ruler. If the four places on the ruler are accurate, then you should have a fairly accurate ruler. However, many labs make their own calibrators, and there is no way to know how accurate the ruler really is. There is no outside agency auditing their work. All we have is their word that they are accurate.

In addition, while it is a good first step to be able to build a ruler using water and alcohol, we are not testing alcohol in water in DUI cases. We are testing alcohol in blood. In science, we need to take into account what is known as the matrix effect. Simply put, water and blood are not the same substance. Water does not have red blood cells, white blood cells, plasma, virus, and bacteria. In order to measure alcohol in blood, we need a blood-based ruler. However, law enforcement labs do not actually use a blood-based ruler. This is where the procedures of the lab really make a difference.

Labs will use a known concentration of alcohol in blood and compare it to their water-based ruler. This is known as a calibrator. This procedure may be acceptable if done enough times with an accurate blood based sample.

Here is the problem. There are very few companies that make the blood based alcohol concentrations, they are not accurate, and some labs use only one calibrator (not four like the water-based.) When the blood-based alcohol sample comes from the manufacturer, there is an insert. The insert tells you that the stated blood alcohol concentration is just a target value. It states that the known concentration it is really just a range. For example, I recently had a case with a blood-based control with a target value of .182. However, upon reviewing the insert that came with the sample, according to the manufacturer, .182 could be anywhere between a .166 and a .198. Thus, the ruler used is not as accurate as we would like it to be. That is a tremendous range when we are trying to determine someone’s true blood alcohol concentration. The picture below illustrates what the blood-based ruler looks like with only one this one known value.

As you can see, you can’t build a ruler with only one point on a line. Thus, with using only one known value, your ruler just is not very accurate – unlike the water-based ruler. The less accurate your ruler is, the less accurate your test result will be. Consequently, the true range of accuracy could be significantly greater than even 10%.
 

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Some things in life seem obvious. It is hotter in the summer. It is colder in the winter. The government must get a warrant to stick a needle in your arm before they forcibly take your blood. However, this last presumption has not been so obvious in Arizona.

For years in Arizona, attorneys have been arguing that law enforcement must get a warrant before taking your blood during a DUI investigation. Unless, of course, the person “expressly consents” to the blood draw. However, many Arizona courts have held that, under Arizona law, we should "imply" your consent to the blood test. Thus, there is no need to ask for your consent, nor to get a warrant before taking blood.

In most DUI cases, officers ask the person suspected of DUI if they will consent to the blood draw. The officer will explain that if you refuse to give consent, a one (1) year license revocation will be triggered. Moreover, the officer will likely inform you that they will also get a telephonic warrant, in a matter of minutes, and forcibly take your blood. Consequently, the majority of people do give consent to the blood draw. This scenario is perfectly legal.

However, every year I see a number cases where law enforcement just takes the person’s blood without asking for consent. They merely say "give me your arm" and take the blood. Most experienced DUI officers will not engage in such conduct. Yet this situation keeps occurring. And until now, many courts have upheld the officer's actions.

On September 1, 2009, the Arizona Court of Appeals stated the obvious.  They held that law enforcement must obtain a search warrant to take a DUI suspects blood - unless the person “expressly agrees” to have their blood drawn. The Court reasoned:

Arizona’s Implied Consent Law, A.R.S. § 28-1321, requires the State to obtain a warrant before drawing a blood sample from a DUI suspect unless the suspect “expressly agree[s]” to submit to the blood test. A.R.S. § 28-1321(B), (D) (Supp. 2005).

We hold that the “express agreement” required by the statute must be affirmatively and unequivocally manifested by words or conduct, and may not be inferred from a suspect’s mere failure to communicate clear objection to the test.

In sum, there is nothing “obvious” about Arizona DUI laws.

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Arizona DUI cases almost always involve a chemical test. There is a movement in Arizona towards the exclusive use of blood testing. It is well settled that blood testing is more accurate than breath testing. But how accurate is blood testing? Can it truly determine a person's blood alcohol concentration? I believe that these are reasonable questions to be asked by a person accused of DUI and facing 30 to 45 days in jail.

Under our system of justice we should demand better answers from the government than "because we said so" or "because our lab has the highest standards." Simple conclusions are not good enough in science and they should not be good enough in justice.

So who checks the government's test results in Arizona? The simple answer is the government. They merely claim to check themselves. I have yet to see one Arizona crime lab that conducts blind testing by an independent party.

Here is how the actual process works. In Arizona DUI cases, The government expert will tell juries that they do double check their work. That is, they have a quality assurance program to make sure the blood alcohol test results are accurate. But the government's oversight of their work is not what you my think. Instead retesting every sample, or randomly retesting a portion of the samples, the lab merely does a technical review.

A "technical review" is not retesting. The Government toxicologist usually puts between 30 to 40 blood samples into a blood tester. Then they turn the blood tester on and leave. The blood tester commonly runs overnight and the printed results are reviewed by the government lab person.

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I ran across an excellent post discussing the source code issue.  That is, the fight between criminal defense attorneys and the maker of the breath tester (CMI) to disclose the code used in their breath testers.  CMI will not allow an inspection of the code.  Consequently, it cannot be checked for accuracy.  CMI essentially tells everyone charged with DUI to "just trust us."

Ed Brayton, a journalist and the co-founder of Michigan Citizens for Science, discusses the source code litigation in Florida.

Here's a very interesting case from Florida, where an appeals court has upheld a lower court ruling that threw out evidence from a breathalyzer test in a drunk driving case because the manufacturer of the device refused to release the source code and allow defense experts to analyze the accuracy of the machines.

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Law enforcement's primary method for determining if a person is driving under the influence of alcohol is a chemical test.  That is, a police officer will take a sample of a susect's blood  or breath.  The chemical test assumes that the composition of everyone's blood is the same.  Specifically, the test assumes that all people have the same hematocrit level.  However, this assumption is incorrect.

The hematocrit level, or packed cell volume, is a measure of the proportion of blood volume that is composed by solids.   Whole blood is composed of solid particles in liquid.  the solid portion of whole blood contains: (1) white blood cells; (2) red blood cells; and (3) platelets.  The liquid portion of the blood is known as plasma. 

In this manner, if a man has a hematocrit level of  .51, then his whole blood consists of 51% solids and 49% liquids (plasma).  This solid to liquid ratio will effect the outcome of a blood alcohol concentration test.  The reason is the liquid portion of the whole blood, the plasma, contains water.   Alcohol is more susceptible of being dissolved in water than is the solid portion.  Consequently, the liquid portion of the whole blood will have a higher concentration of alcohol than the solid portion.

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