The testimony of the hanged man

A hanged man would say anything to save his life. But what if his testimony is true? When Inspector Ben Ross is called to Newgate Prison by a man condemned to die by the hangman's noose he isn't expecting to give any credence to the man's testimony. But the account of a murder he witnessed over seventeen years ago is so utterly believeable that Ben can't help wondering if what he's heard is true. It's too late to save the man's life, but it's not too late to investigate a murder that has gone undetected for all these years.