If there was insufficient evidence why is he still in jail? You may not have all the facts so you should speak to his attorney.
Mr. Keller brings up a good point. But to answer your question, you can bring a vivil lawsuit but it is extremely difficult to win. Unlike a preliminary hearing, the burden would be on your boyfriend to show misconduct. He would need to show not only that they did not have a prima facie case but that they knew or should have known that they did not and did this just to basically harrass him. While this may seem to be what happenned, it is nearly impossible to prove in court. You should sit with someone because I do not know enough about these particular facts, but you should be aware of this.
This is not intended as individual legal advice and there is no attorney client relationship established by this answer. It is advisable that you seek individualized legal assistance. This is not a substitute for hiring an attorney.
I'm guessing that this question is related to the one I just posted an answer to. The short answer to the question would be NO. Beyond that, "suing" anyone ought to be the least of his/your concerns. He has an active criminal case in Allegheny County and needs to devote all of his attention and resources to defending against the charges. Consideration of suing someone should wait. Good luck.