It is difficult to provide you with an answer to this question as it is not clear what hearing you are scheduled to attend at this stage (preliminary hearing, status conference hearing, ARD hearing). You would defend yourself at a preliminary hearing but would rarely do so by calling witnesses on your own behalf. You would not defend yourself at an ARD hearing as it is a consent pre-trial diversionary program offered by the district attorney's office. What is clear, however, is that this is a very serious matter that could have a long term effect on your career aspirations and should not be taken lightly. You have likely invested countless hours investing in your education along with the tens of thousands of dollars spent on tuition. You should definitely contact a qualified attorney to insure that you move through this situation in a manner that will not jeopardize your future.
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The other answer provided is true in that without knowing your stage of the proceeding a full answer is difficult. However, I would not bother bringing witnesses as it seems that you will hear about whether or not you will get into the ARD program. Of course you should consider hiring, or at least consulting with an experienced criminal defense attorney, as there maybe other alternatives. Good luck!