One of the few episodes where Perry is absent during the epilogue. Paul and Della explain how Perry solved the case. This is the second episode in a row where Perry is not in the epilogue.
At the hearing, Perry asked the judge's permission to conduct his demonstration of the remote control operation of the gas heater. That's okay for a preliminary hearing where no jury is present. But if it were a jury trial, Perry would need to discuss the demonstration with the judge and the DA out of the jury's presence, preferably in the judge's chambers, so the judge could determine whether the demonstration might unduly prejudice the jury.
The operator of the Harbor Patrol boat is also visible as a spectator in a courtroom scene.
Raymond Burr was ill during the time this and the previous episode were filmed, so the production had to shoot all the scenes that he wasn't in and wait for him to return. That's why he's not in the final scenes. Notice also that in the courtroom scenes, he doesn't approach the witnesses as he usually does. When he asks a question, he does it in a closeup. He's not in any of the wide shots of the courtroom scenes.