As a Denver DUI lawyer, it is always interesting to see prospective jurors expectations about forensic evidence. The ones who watch shows like CSI always expect a great deal. However, reality tends to be a huge let down. Blood alcohol testing SHOULD be as precise as TV labs portray it. Unfortunately, these labs are overworked and often cut corners on procedures, training, record keeping, etc. Colorado's own state run lab was shut down over just such issues.
It is the job of the DUI lawyer in Colorado or anywhere to vigorously challenge the prosecution's evidence. Sometimes we find such problems as this story
from Florida where the lab supervisor was actually stealing evidence from the lab to supply his own narcotic addiction.