If a student is found responsible for sexual assault at his or her college, it depends on the sanction as to whether there would be a mark on a person's transcript. A mark on a person's transcript, however, may be the least of one's concerns at that point. If found responsible for sexual assault, potential consequences often would include at a minimum suspension, if not expulsion, depending on the severity of the act.
There's a difference between an academic transcript and a disciplinary record at most schools. The academic transcript is, as it sounds, it's the record of the person's academics. If a person were not to be suspended or expelled, there may be no notation on the person's academic transcript. There would be a notation, which can both be either expansive or limited in scope on the person's disciplinary record. The disciplinary record is different than the academic transcript, and it becomes more nuanced yet in terms of what would be requested in given circumstances, be it by a future school, graduate school that is, professional school, employer, the military, whatever the case may be.
You need to make sure that your interests are protected so that you can avoid a finding of responsibility so that you're both short-term and long-term goals are not affected. An experienced attorney advisor can help protect your interest in that regard.