I watched the video. Ever since the video of Terri in the garage, I've been unsure about what to make of her stoic expression and complete silence. It is not a stretch to assume that her attorney told her to look straight ahead, don't smile, don't answer, etc.
When DS came out of the courthouse and wasn't stoic, several believed she was smirking and smiling too much.
If Terri did smile or looked like she was relaxed, she would be accused of reveling in her crime and the fact that for now she's getting away with it. However, IMHO, her look is so affected. She seems very concentrated on not having any sort of facial expression. Also, I wonder if she's on medication. Innocent or not, the strain has got to be nearly unbearable.