A 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 am 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.
But here is the problem, the law gives the prosecution a presumption that your BAC was the same at the time of driving as when it was collected as long as it is collected within 3 hours of driving. This presumption is rebuttable however, which means if credible scientific evidence is presented then the finder of fact can conclude your BAC was lower. This is where the expert comes in. He or she can render an opinion that the BAC was lower at the time of driving and if this testimony is accepted can mean the difference between a dismissal or a conviction.