Answer is Double Jeopardy: Emily has already been tried for the murder of her husband. She was acquitted as not guilty for the reason of "sleepwalking" as a side effect of the drug.
Jonathan realizes that he was played by Emily and Victoria. He wants his revenge. He tricks Emily into thinking that Victoria has spilled the beans on the insider trading. Emily wears a wire and goes over to Victoria’s and makes her say sufficient details that incriminate Victoria in insider trading.
Now that he's taken down Victoria, he plans his revenge on Emily. By law she needs to be under his care because of her "condition". He prescribes some drugs with some insane side effects to Emily. She throws a fit and Johnathan declares that Emily is no longer fit to be under his care and that she’s taken back to the mental ward for refusing treatment. Over some time there based on her treatment, Emily eventually becomes zoned out and loses her mind because of all the medication.
This way Johnathan orchestrates a punishment for both the women, and gets his life back.