This is not the defence scenario.
This is Nevill was shot in bed & then went downstairs to ring Bamber.
The prosecution saying he would not have been able to speak.
The fact the defence at trial was unable/unwilling to correctly interpret the soc evidence by way of blood stains/lack of, casings, distance of shots, trajectories and wound tracks does not make it any less relevant. It is further evidence of a poor defence.
It can be evidenced the perp was in the main bedroom shooting June when NB appeared on the landing at the entrance to the main bedroom and sustained his facial shots. This supports NB coming upstairs from the kitchen having called JB.