Sam and Dean traveled to Canton to investigate the death of Cal Hawkins, who died of injuries consistent with a head-on collision, but was found in what was thought to be James Dean's vintage Porsche parked in his own garage. When they approached Sheriff Carnegie regarding his investigation of the death, he confidently told them that the guy that did it had already been booked.
He proceeded to show them his proof, which was a video shot by his best friend, Jim Grossman, which really only proved that Jim was horrified when he discovered his best friend's gruesome death scene. "Psycho taped his own handiwork," the sheriff declared. Plus, he noted, Jim was the only one around for miles when Cal was killed. Confused by the sheriff's reasoning, Dean asked him to explain how Jim could've slammed Cal into a windshield with all the force of an 80 mph crash. The sheriff suggested maybe it was drugs. Aware that they were dubious, he dispensed a nugget of wisdom: "You know this ain't brain surgery, boys! Whatever it looks like, that's what it usually is. It's simple."
When Sam and Dean next encountered Sheriff Carnegie at the scene of Civil War expert William Hill's mysterious death, he was a bit rattled but still certain that a close examination of the facts would result in a reasonable explanation, as always. Sam asked him what reasonable explanation he could offer for the gunshot wound to the victim's head with no evidence of a gun, gunpowder or bullets. Trained assassins, like in "Michael Clayton", was his assessment. He invited them to have a look around the scene for themselves, but warned they wouldn't find anything because professional killers never leave fingerprints.
When Sheriff Carnegie was challenged with the abduction of a girl by someone her friends swore was Paris Hilton, he was finally at a loss for a reasonable explanation and could only shrug and say he didn't know. After eliminating the culprit they discovered to be Leshi, the Winchesters received a call from Sheriff Carnegie on their way out of town. To their amusement, he'd put an APB out on Paris Hilton.