Amber Frey: Witness for the Prosecution (2005)

Traveling salesman Scott Peterson quickly charms Amber Frey after a single blind date. When a coworker learns of their marriage, Amber believes Scott's wife has died. It is later revealed that his wife is actually alive and missing, pregnant with their child. Amber, also pregnant, hears reports of Scott's wife and baby being found dead and secretly records his phone calls for the police. She becomes the crucial witness in his murder trial.