Salvation of a Saint by Keigo Higashino

Toyko businessman Yoshitaka Mashiba is found dead in his home, poisoned by some coffee.  The prime suspect is Mashiba's wife, Ayane, but she was away for the weekend, visiting her parents in Sapporo. Ayane's apprentice in her quilting business, Hiromi Wakayama, found Mashiba and called the police.  It seems they were having an affair.  Detective Kusanagi feels that Hiromi is their prime suspect, while his female colleague Kaoru Utsumi feels that Ayane is responsible-- although proving her guilt will be extremely difficult. The reader knows, however, that Ayane did the deed. With the help of professor Manabu Yukawa, whose nickname is Detective Galileo, they hope they will succeed.  Salvation of a Saint is the second book to feature Kusanagi and Yukawa.  It's a real treat for people who enjoy a good puzzle and the intricacies of trying to prove guilt.