Final answer:
The trial of Maurice Papon and subsequent media pressure resulted in a re-examination of the police files relating to 17 October 1961.
Step-by-step explanation:
The correct answer is: 3) The trial of Maurice Papon and subsequent media pressure.
The trial of Maurice Papon in the 1990s led to a re-examination of the police files relating to 17 October 1961. Maurice Papon, a high-ranking French official during the 1961 Paris massacre, was tried for his involvement in the event. The trial brought attention to the police's actions during the demonstrations and resulted in increased scrutiny of the police files from that period.