French prosecutors dropped an investigation into former IMF chief Dominique Strauss-Kahn on Thursday, saying they had evidence of sexual assault but that the case was too old for them to prosecute. Tristane Banon, a 32-year-old author, claimed the politician tried to rape her in 2003, but prosecutors said the evidence suggested only sexual assault -- which has a shorter statute of limitations -- rather than attempted rape. Duration: 01:00