Sexual assault cases rank among the most difficult to prosecute, as the one against ex-IMF chief Dominique Strauss-Kahn is demonstrating. Held under house arrest since being charged with sexual assault of a maid at a New York hotel, the French politician was released on his own recognizance Friday amid questions about his accuser’s credibility. The “he said, she said” nature of such cases is one complicating factor (as is getting victims to report sexual assaults in the first place). But so are prosecutorial zeal, power politics, personal troubles of accusers, and even false accusation. Here are five high-profile sex-crime cases that fell apart, in which one or more of those factors played a role.