Who decides whether someone should be charged with OWI? Normally an officer on the scene of the traffic stop will make that determination. That officer is the person who observes the driving and the behavior at the scene and ultimately requests a sample for blood alcohol analysis. The arresting officer is often times the only witness the State uses in an OWI prosecution. Before they finish their training to become a police officer, all officers are taught the necessary testimony to obtain an OWI conviction. In some cases, an officer does not make the final charging decision and will request that a prosecutor review the evidence. Even if the officer told the driver that they were not going to be charged with OWI, the prosecutor can file the charge. In every case, the prosecutor has the ultimate decision on whether to proceed with a charge and pursue it in court.