An attorney's involvement in an academic misconduct hearing at a college or university will depend on several factors. For one, the attorney would not necessarily be able to serve the role of an actual attorney, they would be able to serve the role of an advisor in most instances, that will also depend on the specific school in question.
At a public college or university in many instances, that attorney is allowed to be involved every step of the process, including at a disciplinary hearing. At many private schools, but not all, an attorney's role or an advisor's role is more limited in scope. That being said, even at schools where an attorney advisor is not necessarily allowed to directly participate, having that experience and knowledge as to what needs to take place in a given case to mount the strongest possible defense and how to navigate what could be a difficult and nuanced process and also to do what's needed to try to ensure a fair process. That would be the benefit of having an attorney advisor in your corner from as early as possible in the process.
More directly, it will depend on the school in question. Regardless of that, an attorney advisor can help in various other ways and it should be involved in any case where there's an allegation of academic misconduct and the person is trying to achieve the best possible outcome.