An obese man's attempt to re-write the "Twinkie Defense" failed yesterday when a NJ jury found him guilty of murdering his son-in-law — despite claims that he was too fat to commit the crime. Williams Ates, 65, was convicted of slaying Paul Duncsak in 2006, then driving 21 hours to his mother's house in Louisiana for an alibi. Prosecutors argued that before killing Duncsak, who was involved in a bitter custody dispute with Ates' daughter, Ates "bought books detailing how to build a gun silencer [and] did Internet searches on how to pick locks and how to commit the perfect murder." The defense said the 285-pound Florida native couldn't have sprinted upstairs and accurately shot the victim — or driven all the way to his mother's home without frequent breaks. He will be sentenced next month.