Boris Nemtsov, my longtime friend and colleague in the Russian opposition, was murdered in the middle of Moscow on Friday night. Four bullets in the back ended his life in sight of the Kremlin, where he once worked as Boris Yeltsin’s deputy prime minister. Photos showed a cleaning crew scrubbing his blood off the pavement within hours of the murder, so it is not difficult to imagine the quality of the investigation to come.

Vladimir Putin actually started, and ended, the inquiry while Boris’s body was still warm by calling...