A dirty license plate proved costly for a Butler man last month.

Walter S. Kradel, 32, was driving his pickup truck on West Cunningham Street in Butler about 1:35 a.m. Dec. 28 when his license plate attracted the attention of a trooper, state police said.

The tag was obscured due to dirt, which is a traffic violation. The penalty is a $100 fine.

Police stopped the truck for the seemingly simple infraction.

But the trooper, in speaking to Kradel, smelled a “strong odor” of alcohol coming from him, according to court documents.

Additionally, the officer noticed an open can of beer on the floor of the vehicle and an open pack of beer on the middle seat.

Police also learned Kradel had a suspended driver’s license from a previous drunken driving case.

A check of his criminal record showed he has two prior convictions for driving under the influence.

Suspected of drunken driving again, Kradel was taken to Butler Memorial Hospital for a blood test. The toxicology report later showed his blood-alcohol level was 0.154 percent, or nearly double the state’s 0.08 percent limit.

Police on Friday charged Kradel with DUI, driving with a suspended license, driving with an open container of alcohol and driving with an obscured license plate.