The Florida Times-Union reports jurors deliberated less than five hours before convicting Coty Wayne Rodriguez on Saturday in the death of 19-year-old Matthew Taylor Roberson.
Prosecutors say both men had been out drinking in August 2010 when Rodriguez's pickup truck crashed at high speed into a railroad crossing signal.
Roberson died of a massive head injury.
Though Rodriguez's blood alcohol level was later found to be within legal limits, jurors convicted him of drunken-driving anyway because he was 20 at the time of the crash and still too young to legally drink alcohol.
Rodriguez claimed he wasn't driving the truck.