In every DWI case a defense attorney must assess two issues - first, was the client intoxicated and second, was the client operating a motor vehicle. Most trials involve the issue of intoxication as the motorist was stopped by a police officer after that officer had seen the motorist violate some provision of the transportation code.
During voir dire, prosecutors attempt to lower their standard of proof by convincing prospective jurors that being intoxicated is more akin to having a buzz than it is to being drunk.
Rare is the case that turns on whether or not the accused was operating a motor vehicle. We've all seen news accounts of the man arrested for driving a recliner (with a motor) down the street while drunk and of the man arrested for being drunk while riding his lawnmower down the road. There was even an unfortunate guy out in Austin was arrested for DWI because he was drunk while riding his horse down the street.
Then there's the instance in which someone is sleeping behind the wheel of a car with the engine on. Sometimes the car is in a parking lot or on the side of road. Sometimes the car is sitting at an intersection. Sometimes the transmission is engaged and the driver has his foot on the brake.
Chad Murray was sleeping in the front seat of his truck with the engine running and the transmission in park. He was parked in a private drive with the wheels on one side sitting on the shoulder - no part of his truck was on the actual road. There were no cans or bottles of alcohol in or near the truck but Mr. Murray was apparently intoxicated (though that was not an issue on appeal).
When questioned by police Mr. Murray did not admit to driving.
A Hill County jury was convinced that Mr. Murray had been operating his truck and they found him guilty of driving while intoxicated. Mr. Murray then appealed his conviction to the Amarillo Court of Appeals arguing that the evidence was insufficient to support the conviction, namely that there was no evidence that he was operating a motor vehicle.
In Murray v. State, No. 07-13-00356-CR (Tex.App.--Amarillo 2014), the Appeals Court found in favor of Mr. Murray, reversed his conviction and rendered a judgment of acquittal. The Court did agree that it was reasonable to infer that at some point Mr. Murray had been operating his truck - but the Court pointed out that there was no evidence that he was intoxicated when doing so.