That feature is "Moonlight Sonata Killing", which is the first one-hour feature of all Conan TV editions. The process is exactly what LZ said. In later famous killings, Hattori told Conan that it would be better if the criminals committed suicide. Conan said, if we detectives cornered the murderers and finally let them commit suicide, what's the difference between us detectives and murderers? Hattori said that only you, a perfectionist, can say such a thing. Conan was very emotional and said, I have killed people and I have always regretted it. I'm talking about an honest doctor.