From Marty's April 14,1981 interview with Crim and Bradley:
Smartt: I was gone all day yesterday was in Reno
Glenna Meeks on the documentary (I hesitate posting anything said 28+ years later but this has been the source of a lot of confusion) so this is straight from the source of that confusion:
Glenna Meeks: Well, Marty had went to Reno the day after the murder, and he came home about 5 or 6 o'clock - it was in the afternoon.
It is clear that Marty went to Reno the DAY AFTER the murders (Monday not Sunday). A lot of speculation has been made on Marty "sneaking" out of Keddie around noon on Sunday headed to Camp 18 with Tina's body when it actually appears that he went to Reno on Monday. So are we really supposed to believe that he patiently waited around till Monday to retrieve Tina's body from that "shallow foliage-covered gorge just next to a rarely-used dirt access road"?