Did you know that your blood is not even really tested for alcohol? What is actually tested is the “headspace gas” above the blood in the vial containing your blood. The basic idea is that when the blood is heated the ethanol (alcohol) molecules that are in your blood will evaporate into a gas into the headspace of the vial above your blood. This will occur until equilibrium is achieved, and the ethanol molecules in your blood are equal to the ethanol molecules in the headspace gas above your blood. Thus, there is a direct correlation in the amount of alcohol in your blood and the amount of alcohol in the headspace gas above your blood. Therefore, by determining the amount of ethanol in the headspace gas, the amount of alcohol in your blood can then be determined based on a formula. This is based on Henry’s Law, that at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. In order to determine how much ethanol is in the headspace gas, the crime lab uses a process called Gas Chromatography. During this process, a sample of the headspace gas is run through an instrument called a gas chromatograph. Many factors can affect the accuracy of the results of the blood analysis. Likewise, there are many errors that can lead to inaccurate results. It is important that your attorney understands this process and knows what errors to look for when fighting a DWI where there has been blood analysis. Just because there is a blood test in your case does not mean you have to settle for a guilty plea!
In 2014, Jefferson County started doing mandatory blood warrants in all DWI and intoxication cases. There is a Judge on call (day and night) to sign a warrant to take your blood if you refuse to consent to a blood test. However, the police MUST HAVE PROBABLE CAUSE to get that warrant. The police officer has the choice whether to ask you for a breath or a blood test, and they now have the capabilities to obtain a warrant in any case where you do not consent (as long as they have probably cause).
It is true that if you refuse to consent to a breath or blood test your license will be suspended for a longer period of time than if you consent, however, why help the police build a case against you? If you consent, and there was no probable cause to take your blood in the first place, the police may still be able to use those results against you. Voluntary consent may remove the taint of an illegal arrest. Evidence that was illegally seized (without a warrant and without probable cause) may still be admissible against you if your consent was deemed voluntary.