>> reporter: and it was a hunt the prosecution said. the investigator told the jury he'd used cellphone data to track the moorers' movements. in the days before the disappearance, they showed up near heather's workplace, some of the bars she liked, even her home. the prosecution suggested the couple was stalking her. then in the early hours of december 18, 2013, with heather's roommate out of town, the prosecutor said the couple struck. it began here. the prosecutor showed the jury surveillance video of sidney walking into a walmart and purchasing a pregnancy test for heather. >> soon as they leave from walmart, they go and call her. why? 'cause the test is for her. >> reporter: the prosecution's theory was that sidney had called heather to come and get the test. take it and then meet up with him later at the landing. they said what she didn't know was that tammy would be there too. >> there's no doubt sidney is