Did Socrates have any witnesses in his trial and if he didn't why was it seen as unconventional?

No...Socrates purposefully gave a defiant defense to the jury because "he believed he would be better off dead". History goes on to describe a defense by Socrates that explains the rigors of old age, and how Socrates would be glad to cirvent them by being sentenced to death. It is also understood that Socrates also wished to die because he "actually believed the right time had come for him to die".