In a handwritten letter sent to Judge Bart Stanley, the teen accused of gunning down a Mt. Leo man during a botched robbery attempt says he is ready to accept 25 years in prison and save the state the trouble of trying him for murder.“I made a terrible mistake,” admits Sam Brinkley, 18, in a handwritten letter reportedly sent from his jail cell asking the court to consider a no-contest plea from him.“It would stop all proceedings and loss to the state,” said Brinkley, noting the state would save money by offering him a deal. “I’m at the mercy of the court.”Brinkley soberly admitted his young age is no excuse for what happened.“Young and dumb won’t fix this, but I live with it every day and I am very sorry,” Brinkley said, signing his name to the bottom of the handwritten document that is now part of his official case file.Brinkley faces life in prison for killing Oswaldo Luna, 43, in January after he and friends went to the victim’s trailer with plans to rob him of marijuana.