Criminal Law Questions? Ask a Criminal Lawyer.
I think I understand now. You ask if you could be arrested for identity theft. The answer to that is simply ... yes. However, I do not think you could be successfully prosecuted for identity theft, or even using an alias at this point for a couple of reasons. First, unless they filed the charges years ago it will likely be barred by the statute of limitations. Second, you generally have to be prosecuted for events arising out of the same criminal episode (if the state is aware of your conduct... which they were) at the same time.
What I'm saying to you is that it is likely that if they were going to charge you with using your sister's name, they would have already done it. Can I guarantee you that they will not attempt to prosecute you for using an alias name? No. But I find it very hard to imagine someone taking that much of an interest in the matter after all these years.
The way to avoid any potential problem in this situation is to contact an attorney in that district and have them do the expungement for you. This would likely cost very little and would prevent any unpleasant surprises (warrants popping out of nowhere). You should contact an attorney and have them file this paperwork on your behalf. They can also give you an opinion as to any residual exposure they see for the events of 1997.
I am not your attorney. Therefore no attorney-client relationship exists and any communications on this website are not subject to the attorney-client privilege. For this reason, please do not divulge any personal information and use this site only for hypothetical questions. This forum is for general questions and answers and I cannot provide you with applicable law or legal opinions or advice in your jurisdiction. Please seek the advice of a competent attorney in your jurisdiction. While I can answer general questions and discuss general legal principles, I cannot give you legal advice in your state. The internet is a great place to get general information but should not be seen as a substitute for the attorney-client relationship or the services of a good lawyer in your state.