The primary determining factors of DUI are whether the defendant was driving, whether what he was driving was a motor vehicle, whether he/she was on the road, and most importantly whether he/she was intoxicated. While some are more easily determined than others, the most vital question appears to be whether the defendant was actually intoxicated. This issue is at the core of the argument and presents the biggest challenge in dealing with the DUI statute.

Recently, new DUI statutes have been enacted to avoid this complicated intoxication issue. These statutes augment the law by not requiring a demonstration that the defendant was under the influence. Instead, the proof rests on a mere reading of a machine to determine the culpability of a suspected DUI driver. These statutes, often referred to as per se, define DUI as driving a motor vehicle on a road or highway with a blood alcohol level of approximately .1. The actual legal blood alcohol level varies from state to state.