There is DNA evidence, photographic evidence, and witnesses. The only evidence missing is the murder weapon, and I don't think it matters very much since she already said she killed him. Her story is that she was a battered woman who snapped, but this doesn't hold much water because she never lived with him, dated him for less than half a year, hadn't seen him face to face for over a year, and drove over a thousand miles on a secret road-trip to kill him.
The person needing evidence at this point is Jodi, herself. She needs emergency room records, police reports, or at least witnesses to the intolerable abuse she suffered over the course of months -- and I don't think she has it.