A riding lawn mower may have four wheels, a powerful engine and can cost as much as a used car. If it's stolen, however, the Georgia Supreme Court concluded Monday that it's not a motor vehicle.

The 4-3 decision overturned the conviction of Franklin Lloyd Harris, who was convicted of felony motor vehicle theft after he loaded a Toro riding mower in 2006 from a Home Depot in Dalton into his van and sped away. Because Harris was a repeat offender, he was sentenced to 10 years in prison.

Public defender Michael McCarthy told the justices that while Harris should still be charged with theft, he shouldn't be punished as if he had stolen a car. A riding mower is many things, a modern mechanical marvel among them, but McCarthy said it's not a motor vehicle under state law.

Prosecutors countered that the state defines a "motor vehicle" as a "self-propelled" device, and there's no doubt a riding mower meets that standard.

The state's top court agreed, concluding in an 18-page decision that the sentence should be overturned because the purpose of a riding mower is to cut grass, not transport people.