I think there were two sets of photographs Roch. I can't understand why some photographs had been hidden from the Defence until 2004 which is unacceptable,as is the destruction of other forensic evidence such as Sheila's nightie which I think was in 1996.
As for Jeremy and his shooting of Sheila,he can't hang around and wait until he knows she is dead because the clock is on him and this is one part of the plan which he couldn't rehearse. He just has to get back to Goldhanger through farmland,erase the tape which has the phone call he made to himself from the kitchen at White House Farm,then waste as much time as he can hoping that by the time the Police enter that Sheila is dead.