If you turn Carl in to Guard Captain Rodney (one of the options for the Skeletons in the Closet quest), he will be incarcerated in the guard jailhouse where you may talk to him.
|Spoiler: Carl's Writings|
Reading Carl's journal and the All but Illegible Scribble found in Jackson Dungeon, you find that Carl is a deeply disturbed individual. Not only did he kill Booth for sleeping with Dana ten years ago, but later he dug Booth's body up intent on putting it in one of Dana's dresses one night while drunk.
On the farm: "Right good day fer farmin' this! Right good day anyday!"
In jail: "I'll be out of 'ere in no time! All I need is a spoon and a zepp'lin pilot's uniform! "