A piece of a man’s mechanical voice box found at the scene of a murder has been the key piece of evidence that will put him in prison. The prosecutor says Freddy Thomas Junior stabbed his former girlfriend to death in University City last year and left her body in a city park. But in dumping her body in the park, he apparently broke off part of the mechanical device that was implanted while Thomas was recovering from a throat cancer operation. Thomas has pleaded guilty to second degree murder. The detective who found the voice box piece has been named the University City detective of the year.