Beckwith gives himself away.
During DeLaughter`s opening statement, he says that the person who committed this murder was a coward. Then you see in the background Beckwith makes a gesture that indicates this is nonsense.
But then he is unconsciously admitting he is the murderer, because he feels he has to defend himself. "I`m not a coward". He knows the prosecutor is speaking about him. If he was innocent, or at least going to act innocent, he shouldn`t have done anything, because he wouldn`t know the real murderer.
If I had been in the jury and seen that, I`d know he was guilty.