We can find the answer to your question in Book II Chapter Two of this excellent novel that gives us a literary treatment of the French Revolution. Treason of course is and was an incredibly serious charge, as it indicated that you had worked against the crown to try and overthrow it in some form. During the time in which the novel was set, the brutal punishment reserved for those who committed treason was to be hung, drawn and quartered. A bystander next to Jerry Cruncher can give us a better description of what this process actually involves:
"Ah!" returned the man, with a relish; "he'll be drawn on a hurdle to be half hanged, and then he'll be taken down and sliced before his own face, and then his inside will be taken out and burnt while he looks on, and then his head will be chopped off, and he'll be cut into quarted. That's the sentence."
Clearly, therefore, the punishment designed for those convincted of committing treason is designed to be particularly terrible to act as a deterrent to prevent anyone from thinking of doing such a crime for fear of what would happen to them.