Clouds of Witness: Lord Peter Wimsey Book 2 by Dorothy L Sayers
The Duke of Denver, accused of murder, stands trial for his life in the House of Lords. Naturally, his brother Lord Peter Wimsey is investigating the crime - this is a family affair. The murder took place at the duke's shooting lodge and Lord Peter's sister was engaged to marry the dead man. But why does the duke refuse to co-operate with the investigation Can he really be guilty, or is he covering up for someone 'She brought to the detective novel originality, intelligence, energy and wit.' P. D. James