the form. >> two years after the murder, virginia and b.j. mcginnis were arrested and charged with donna hartman's murder. virginia now claimed she wasn't at the scene of the accident and as proof, she reminded prosecutors she wasn't in any of the photographs. but one of the photographs showed the shadow of the photographer. was it possible for science to identify the photographer from the silhouette? >> we knew what day it was and we knew what time it was because we had the 911 call. that gave us the position of the sun. and with the position of the sun and the distance to the rocks, we were able to do the old high school pythagorean theorem, a squared plus b squared equals c squared. >> the distance between donna and the photographer was calculated by analyzing the millimeter of the camera lens. by measuring the length and angle of the shadow and determining the exact location of the sun at the time the mcginnises called police, investigators reached an interesting conclusion. the photographer was 5'6" tall, the same height as virginia