Haha, because that would mean Casey has some reason and common sense, silly!
No, but seriously, I don't know. Daily I go back and forth from accident to willful negligence to premeditated murder and back again.
One correction on your comment though - I don't necessarily believe that she would have been "accidently" left in the car. This could have been planned too.
One thing we all know though, is that Casey is willing to take a lie to the bitter end. Even a rediculous one. Also, she's got a lawyer who is determined to make a giant spectical of a trial.
Additionally, I think her lawyer knows that no one trusts her. He's not going to let her change her story now. He's going to concentrate on attacking the evidence and trying to get a full acquittal. If she admitted it was an accident, then she is admitting she had something to do with the death and she will still do jailtime just based on her actions up to this point. I think she honestly thinks JB is going to get her out of this so why would she admit that she did have something to do with the death?