Smart & Aggressive
attorneys defending you.
click for a free consultation

Blood Draw Issues in AZ DUIs: Why the Amount of Blood Drawn Matters

Posted on July 19, 2011 in BAC

Time and time again in Arizona DUI cases, I have seen a very real, recurring problem in the blood testing that occurs to determine the BAC (blood alcohol content) of the person accused of a DUI. The problem lies with the amount of blood drawn from the person.

In order to understand why a problem can arise with the amount of blood drawn from a DUI suspect, it is important to understand how a person’s blood is drawn in DUI cases. In Arizona, when blood is drawn, it is almost always drawn into two separate grey top tubes. The blood is drawn into these tubes using vacuum technology, so the blood is literallysucked through the needle and into the tube. If manufactured correctly, these tubes have two salts already in them. These salts are there in specific quantities to make sure that the blood: 1) doesn’t clot, and 2) doesn’t begin to putrefy. However, because of the vacuum seal, there is no way to test each tube before it used. Furthermore, there isno way to reduce the amount of salt within the tube if a smaller amount of blood is sucked into the tube than expected, and this is where our problem arises.

Specifically, a problem can occur when one doesn’t put enough blood in the tube, as the amount of salt present in the tube is supposed to be at a certain ratio with the blood. The problem is akin to putting a fixed amount of powered drink mix in a glass, expecting to pour in approximately 8 ounces of water; however, for an unexpected reason, you onlypour in 4 ounces of water. The drink mix is too concentrated at that point, and it doesn’t taste right. That is similar to happens in the blood tube when too little blood is put into the tube- there is too much salt present in the tube.

The science behind the testing of a DUI suspect’s blood for BAC is somewhat complicated, but having too high of a concentration of salt disproportionately affects certain types of molecules- including alcohol molecules. This incorrect ratio of salt and blood can cause drastically inflated BAC results (meaning that the test will say that the person hadmore alcohol in his or her system that he or she really did). In essence then, when the Police or phlebotomist doesn’t draw enough blood into the tube, the BAC results for that person will likely come back higher than they are.

Obviously, an erroneous BAC level can have a serious impact on a person’s DUI case in Arizona, as it could result in a higher charge (such as Extreme DUI if the BAC is .15 or higher, or Super Extreme DUI if the BAC is .20 or higher), and is an issue that should be examined by a skilled Arizona DUI defense attorney.

Contact Us


  • All fields required *
  • This field is for validation purposes and should be left unchanged.
  • This field is for validation purposes and should be left unchanged.