. >> how do you know it is andrea benson?gistered to her. >> you can read a license plate with those cameras? >> pretty good. >> directives obtained data dumps in washington, d.c.. that allowed them to map the travel of the cell phones as they pinged off the towers. >> can you follow the cell phone? >> followed her around washington d.c. simultaneous with andrea's, they were together the entire day. >> violet friday, the night peggy was murdered, diana's phone stopped moving and went quiet. but andrea's phone? >> we saw andrea's phone head out of the washington area and head up i-95. plea exactly the way you drive if you are heading for peggy's house. along the way, the tracfone was activated and at 1:17 a.m. it pinged a cell tower right near peggy's house. what was going on? was this murder for hire? did andrea benson drive up to new york, call peggy on the tracfone, somehow get to her house and murder her? assistant d.a., moran, did not think so. peggy would never have let a stranger like andrea benson into her house. >> so