"DUI case can be quite complex when it comes to the chemical test aspects of the defense. Both breath and blood tests often involve very unique scientific calculations that are difficult for the laymen to understand. This is where an expert can help. The most common experts used in a drunk driving defense are forensic toxicologists who specialize in the interpretation of an individual’s blood alcohol level at a given point in time. You see the breath or blood test you took will only tell you the level you are at when the sample was collected. However, what is important is what the BAC was at the time of driving This is where a toxicologist can assist the attorney. No one’s blood alcohol level remains constant over time, it changes, either going up or down within a certain period of time. Importantly, when a person has drank alcohol close in time to the stop, he or she will usually be rising which means their particular BAC will be lower at the time of driving, this helps the defense. Adjudging what a true blood alcohol level is at a certain time involves complex formulas that take into account absorption rates, burn off rates, and metabolism."
In addition to issues of rising blood, many cases involve situations where a cop or other person does not follow the proper procedures when collecting a blood or breath sample. For example, the phlebotomist may fail to properly disinfect the puncture site or the collection might violate other state regulations. Here, as well, an expert can be used to show how the procedures were not followed and explain why the violation affects the integrity and reliability of the sample. Hiring an expert can also be helpful in raising other defences such as contamination of a breath test by mouth alcohol or people that suffer from medical conditions such as GERD.