The documents in the case

The Documents in the Case is a 1930 novel by Dorothy L. Sayers and Robert Eustace. It is the only one of Sayers's twelve major crime novels not to feature Lord Peter Wimsey, her most famous detective character. However, the forensic analyst Sir James Lubbock, who appears or is mentioned in several of the Wimsey novels, also appears in The Documents in the Case. (This summary is from Wikipedia.)