New Jersey DWI Attorney John Menzel

What Is The Procedure Of A Blood Draw In a DWI Case?


The question about whether an officer is going to take blood or breath usually arises in the context of a motor vehicle accident, or for some other obvious condition that makes breath testing the improper way to measure blood alcohol content. When that occurs, police are generally required to get a warrant from a judge. They can do this by telephone. There are standard forms that they can fill out to indicate why they have probable cause to believe that the blood will provide them with relevant evidence. Probable cause simply means that the officer demonstrates that he has enough information on which to justify continuing his investigation. This is not a question of whether the person is guilty or not guilty, only whether the officer has sufficient reason to engage in a practice that’s very invasive, which is the of drawing a blood sample.

There are occasions where an officer will be excused from getting a warrant, such as when the subject consents to a blood draw. This happens too much in my opinion, only because I don’t know why somebody would consent to provide evidence that would get him or her convicted unless they are absolutely certain they’ve had nothing to drink and want to demonstrate their innocence. Again, people have no obligation to demonstrate their innocence. There is not going to be any adverse inference that they had a guilty mind in refusing a blood test, because they have an absolute constitutional right to maintain the integrity of their body, but consent is still the most common way that officers get around the requirement that only a warrant justifies the drawing of the blood.

A second exception to the warrant requirement is something called exigent circumstances. That may arise in the context of a complicated accident scene where people are very busy. Sometimes they don’t smell an odor of alcohol or get an admission to drinking until after the subject is at the hospital. Because alcohol in the blood tends to dissipate relatively quickly over time, if probable cause develops later and there is not enough time to get a warrant, the police can claim exigent circumstances and draw the blood without a warrant. It’s ultimately got to be tested in a hearing before the judge and the judge will decide whether in fact, that officer’s impression was legitimate or not. If it’s deemed to be legitimate, the failure to get a warrant would be excused. If it’s not legitimate according to the judge, then the blood test result would be excluded from evidence.

Once we get through that we go through the actual process of drawing the blood. This has to be done in a medically acceptable manner, and most often a doctor, nurse, or a laboratory technician completes the procedure. It should be done in the presence of a police officer who watches the blood draw. When the person drawing the blood meets the patient, they have to prepare the site where the blood will be taken from by using a non-alcohol soaked cotton or sponge and cleanse the area by cleaning it in an outward spiral. The idea is to push the contaminants and other things away from where the skin is going to be punctured. If they just rub it back and forth they are just moving the contaminants and the dirt back and forth. That can introduce foreign material into the sample that we don’t want in there.

The tube has to be of a certain kind, usually one with a grey cap that contains certain powders, such as an anti-coagulant and a preservative. When the blood is drawn, the nurse, technician, or doctor then has to invert it usually 8 to 10 times to make sure that the anti-coagulant and preservative is mixed throughout the sample, so that it’s homogeneous as possible. You don’t want to shake it vigorously because that will break the little red blood cells and other components in the blood, and alter the composition of that sample for purpose of measuring the amount of alcohol. The sample then has to be properly packaged, labeled and stored as it makes its way from the person’s arm ultimately to a laboratory. There, a chemist is going to take that sample and inject a very small portion into something called a gas chromatograph. The sample is basically vaporized and a light source is looking to see the color of the wavelengths created by the vaporization.

Depending upon the patterns that are admitted, that can create a spectrum, and they use that a lot for drugs. The other way they do it with gas chromatography, where the sample is actually passed through a long tube that is filled with sand. What happens as that sample is forced through that tube, it’s different components separate out. When it gets to the end, it’s vaporized and a detector will see how light is absorbed based on what is emitted from that tube, and identify the substance by comparing it to different standards. What the standards do is similar to putting marks on a ruler. When the sample is put through it, what the sample looks like is compared to those marks on the ruler and that tells us not only what the substance is, but how much is in the blood.

Thankfully it’s a much more technical process and one that often requires a defendant to hire an expert to look for errors in the process. Blood testing is much more specific and much more direct because we are directly measuring the alcohol in the blood as opposed to inferring what the blood alcohol is by measuring breath.

For more information on Blood Draw Procedure In New Jersey, a free initial consultation is your next best step. Get the information and legal answers you are seeking by calling (732) 899-1899 today.

John Menzel, J.D.

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