Though there is much talk of 'doubling' and shared guilt in the novel, Highsmith's well-known misanthropy lets no one off the hook. (...) The film, by contrast, discriminates very clearly between guilt and innocence: despite the suggestions, especially in the first half of the film, that Guy is somehow tainted by or complicit in Bruno's schemes, and that Bruno carries out Guy's unrealised desires in murdering Miriam, Guy remains basically 'good'. At the end of the film he is cleared of all explicit guilt.
Hitchcock worked on an initial treatment of the script with his usual collaborators at this time, his wife Alma Reville and Whitfield Cook. He then hired Raymond Chandler to prepare the finished script. Chandler enjoyed considerable prestige in Hollywood at the time, not only for his fiction and the films made from it such as The Big Sleep (1946), but for his succesful collaboration with Billy Wilder on the script of Double Indemnity (1944), and for his own original script for The Blue Dahlia (1945). After some preliminary conferences, however, relations between the two men began to sour, and Chandler withdrew to work alone, with only occasional input from Hitchcock's.
Though Chandler didn't much like the book, he wanted to remain as close to it as possible and became increasingly irritated by Hitchcock's attempts to move it towards a more voncentional and commercially acceptable formula. Always a prolific letter writer, Chandler complained to his British publisher, Hamish Hamilton, and to friends, that Hithcock cared little for dramatic and character logic and was always prepared to sacrifice these for a striking camera angle or an unusual location ("wanting to do a love scene on top of the Jefferson Memorial or something like that"). Relations fianlly broke down after one of their rare script conferences when Hitchcock overheard Chandler referring to him as a "fat bastard" as he left. Chandler's script was immediately discarded and he was replaced by the relatively inexperienced Czenzi Ormonde, who had worked in a research capacity for Ben Hecht and David O. Selznick, but had no major screen credits on her own. When Chandler saw the final script, he was appalled and wrote a lengthy (but unsent) letter to Hitchcock, in which he accused him of approving "such a flabby mass of clichés, a group of faceless characters, and the king of dialogue every screen writer is taught not to write -the kind that says everything twice and leaves nothing to be implied by the actor or the camera." His veredict on the finished film was equally unkind.
Petrie, Graham. "Transfer of Guilt", en Sight & Sound. Juny 2009