The idea behind the deprivation period is to make sure no foreign substances or foreign objects interfere with the alcohol sensor and throw a "false positive." This includes but is not limited to substances absorbing residual mouth alcohol-- like chewing tobacco or chewing gum. The protocol thus assumes that the machine is not infallible and requires human intervention to ensure its proper use. When officers fail to follow proper protocol, they risk invalidating the results of the science they purport is the gold standard in Iowa Operating While Intoxicated investigations and criminal prosecutions.
