If I was a Lawyer for the defense, I would call upon Jacqueline Kennedy to take the stand. She was the only one exempt from sharing her opinion as to where the shots came from. She obviously was told to not say anything because she was warned that if she voiced what she saw, the country would have been put in chaos when it realized that a coup had just taken place.
She was not allowed to give her account or statement and she was looking right at JFK when the shots came in! She would know the direction the shots came in from - grassy knoll or otherwise! Most people ran up the grassy knoll indicating that it was the likely spot where the sound came from. The initial reporter on the scene said there was a shot like a firecracker and then 2 shots fired in quick succession. What little statements she was heard to say were: "THEY killed him" and "That is not him" - this would indicate that she had a story tell and was muffled. No one is exempt from testimony when someone else dies and you are a witness! Pretty simple defense for LHO and the only person not questioned in the entire matter! The best defense ever!