Once the prosecution ends its' direct of the technician, this is where a trained DUI defense attorney needs to pounce. As an experienced Seattle DUI attorney I have cross examined breath test technicians on many many occasions when challenging the results of a breath test document. The prosecutor's job is done once they get the number in front of the jury, but the DUI defense attorney's is just beginning. What do I mean by pounce, well you need to hammer home to the jury that the alleged numbers are really a probability fraught with uncertainty and the technician will have no choice but to admit the numbers are not perfect. Any measured value has uncertainty, as I understand it, that is how science works! No scientifically produced value is perfect and each measured "subject sample" could be much lower or much higher given uncertainty. Why didn't the prosecutor ask the technician about that and disclose it to the jury? Well, of course they want that precious numbered to be free from any speculation. That is why it is absolutely necessary to discuss that with the technician on cross and to make sure and point out in summation that the prosecutor essentially hid that information from them.
One additional argument I commonly make is that the presumed temperature of the simulator is also based upon skewed conclusions. The simulator solution is a mixture of ethyl alcohol and some type of distilled water to simulate a known value, e.g. .04, .08. 10 or .15. The toxicology lab prepares a simulator solution to be approximately .08 for use in the datamaster. The mixture is tested by several toxicologists an certified for use. The measured value also has an uncertainty and that should also be exposed to the jury, especially if the simulator solution is closer to the .072 to .088 ranges (that is the allowable range of a simulator solution for use with the datamaster). The mixture, for use in the datamaster, must be heated to a known value and the common value is 34 degrees Celsius plus or minus .2. In between a subject's sample, the simulator solution runs into the datamaster for an "external" check to make sure the datamaster is reading a .08 mixture (although if the reading is anywhere between .0-72 and .088 it is acceptable? Really? Anyway, that is an argument for another day). Why is that 34 degrees value important? Well that is the presumed temperature of a person's mouth when exhaling. Again, there are many treatises and experts who agree that 34 degrees is not the correct average temperature of every person, and technician's and toxicologists who testify in DUI trials must agree, there is too much proof to the contrary and science simply doesn't support we are all the same. Here is where it is necessary for your DUI attorney to expose the speculative nature of breath testing. If someone's mouth temperature is lower or higher, invariably the breath test measured on the datamaster will be either lower or higher. Again, in summation it is essential your DUI attorney points out this non-disclosure of information to the jury.
At the end of the day, a trained DUI defense attorney can show that these alleged measured values are fraught with speculation, yet when determining the guilt or innocence of a citizen the government has no problem with presumptions. There are numerous other situations in which a trained Washington State DUI attorney can expose speculative breath tests results to a jury.
If you find yourself in need of a renowned, trial tested DUI Defense attorney, look no further than the Webb Law Firm. Call today (425) 398-4323