cards was going to collapse in trial. >> reporter: in october, 2016, more than two years after the death of his son, ross harris went on trial for murder. >> death. deception. and a double life. >> reporter: chuck boring, the lead prosecutor, told the jury why ross' story had never added up. that chick-fil-a video showed cooper wide awake. that drive that was too short to forget a toddler. the car seat was just inches behind ross. and at ross' office there was a photo of cooper and a gift from cooper. he even sent a text to leanna in the afternoon about cooper. when you getting my buddy, it said. none of that jogged his memory? >> there was just cue after cue after cue that if he had actually forgotten would have triggered something. >> reporter: and then the prosecution showed what it believed was powerful evidence that ross had to have known that cooper was still in the backseat.