Because invalid breath machine tests can make it more difficult to obtain convictions, many law enforcement agencies now prefer to obtain blood samples. While it’s true that blood results are harder to attack, the methods used to obtain them are not. My strategy is to attack the method used to obtain the results thereby damaging the results’ validity.
Most people, left to their own devices, would never consent to having their blood drawn after a DUI. It could be a health risk for some such as hemophiliacs. Some are afraid of needles and even others follow a religion that specifically prohibits blood being drawn.

All things considered, I generally advise my clients to refuse giving blood for the purpose of testing their blood alcohol content. I maintain that medical professionals have a duty to respect the wishes of their patients regarding their own bodies and that the same rule must apply to law enforcement agents. The Hippocratic Oath requires physicians to put their patients’ needs and desires first, to defend their patients’ privacy and to respect their decision to decline medical procedures.

I challenge blood test results on that very basis. I maintain that blood was drawn against the person’s will and that drawing blood over a person’s objections is committing assault and battery. Please realize that a police officer that wishes to draw your blood must either have your consent or obtain a warrant from a magistrate.