No double jeopardy
This movie is correct, double jeopardy only applies when the Jury acquits the defendant. In this case the judge dismissed the trial due lack of evidence, it was a mistrial. Him pulling the plug of his wife's life support was evidence of his intent to kill her and they had grounds for a retrial.
The movie should have explained this.
http://en.wikipedia.org/wiki/Double_jeopardy