This professional skepticism earned Houdini the ire of many of his contemporaries, including Sherlock Holmes creator Sir Arthur Conan Doyle, who was himself a staunch believer in supernatural phenomena. Ironically, it was Houdini the non-believer who developed a technique for continuing to debunk pyschics from beyond the grave.
What method did Harry Houdini use to debunk psychics even after his death?
No doubt sensing that his vocal stance against spirit mediums would make him an ideal subject of more theatrical self-proclaimed psychics following his death, Houdini and his wife Bess established a codephrase that Houdini's ghost would use if he was ever successfully contacted in The Great Beyond. If the "spirit" of Houdini never spoke the phrase, clearly the spirit medium claiming contact with Houdini was a fraud.
The codephrase was "Rosabelle believe," a line from a play that Bess herself performed when she and Houdini first met. It was a phrase of personal significance to the couple but one randomly chosen from the play. Thus, no would-be psychics would likely guess the phrase -- presuming they even guessed that there was a codephrase -- by researching Houdini's past.
Bess Houdini continued attending seances for a decade after Harry Houdini's death in 1926 -- and no medium ever reported hearing "Rosabelle believe" from Houdini's ghost. After ten years, Bess declared the matter settled and subsequently revealed Houdini's technique to the world. Thus, Houdini continued to debunk fraud mediums from beyond the grave -- though he might not approve of that particular description of his endeavor.
That's not just some snarky and sagacious psychic-slamming, it's an ectoplasmically ingenious example of the Truly Trivial.