Having sex with someone who is underage (in this case, 17, in a jurisdiction where the legal age is 18) is a strict-liability crime, meaning the prosecution doesn't have to prove that you knew. But be aware that, while Minsky is dead and unable to defend himself, there is apparently a witness who claims that Minsky is innocent--specifically, that Giuffre was directed to have sex with Minsky but Minsky turned her down. Since dead people can't have trials, we will probably never learn the facts of the matter.