The case of Leopold and Loeb is an American case that was almost a perfect crime, but a small detail botched it, and both landed in prison.
Would-be perfect crimes are a popular subject in the movies, and many have been made. A few include Double Indemnity, The Postman Always Rings Twice, Witness for the Prosecution, and Dial M for Murder.
Note that many perfect crimes may have been committed, if there were no public or media knowledge of them. We also note that police are fallible, and some never-solved crimes would be solved, had the police better resources; in the well-known case of Jack the Ripper, evidence was left, but the crimes were never solved.
Some crimes such as the Tylenol scare of 1982 are referred to as perfect, but a possibility always remains that a culprit will be identified.
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