Vincent Brothers was a bad man. Not Shaft bad, but "commit mass murder on your own family and then smugly lie about it in court" bad. In July of 2003, the elementary school vice principal flew from California to Ohio to supposedly visit his brother, but in reality, the trip was his planned alibi. Once he landed in Columbus, he rented a car, drove back to Bakersfield, CA, and waited for his wife to come home with his three children and his mother-in-law. He then shot and/or stabbed all of them to death, including his six-week-old son. Once he finished staging a break-in at the house, he drove the rental car back to Ohio and enjoyed the rest of his trip like nothing happened.
Brothers was immediately suspected once the bodies were found, but authorities couldn't arrest him thanks to that pesky alibi of his. The flight and car rental records seemed to confirm he was in Ohio at the time of the murders, and knives that long haven't been invented yet. Sure, the car's odometer showed that Brothers could have made a round trip to the West, but there was no evidence of that. Maybe he just liked driving in circles for fun.
What happens when you drive down the freeway for a long time? Your windshield picks up all sorts of gross insects. So do other parts of your car, whether you notice it or not. So, investigators asked entomologist Lynn Kimsey to inspect Brothers' rental car -- where she discovered a paper wasp, two species of true bugs, and the leg of a type of grasshopper, all of which are specific to the Western United States. (Translation: Not Ohio.)
On top of that, the lack of any butterflies and the presence of moths strongly suggested that Brothers had driven at night from Columbus to Bakersfield and back again. Kimsey's testimony helped seal the deal for Brothers, who was convicted of mass murder and currently sits on death row. Moral of the story: Always wash your rental car, you goddamn animals.