By adding one substituted bullet (PV/20) which replaced the original shot fired by way of a second weapon, and leaving one bullet unrecovered in the skull of one of the child victims, cops were able to present the case, that 25 shots had been fired, the victims had 25 wounds, there were 25 bullets recovered, and 25 spent cartridge cases - yet because a test fired control round had been introduced to replace one of the two bullets which inflicted wounds to Sheila Caffell's neck (for the purpose of disguising the involvement of a second weapon in the shootings), there were 26 shots fired, and there should have existed 26 bullets along with 26 corresponding spent cartridge cases, for example, the 25 shots that were fired at the time of the shootings, along with the corresponding 25 spent cartridge cases, + the control bullet and it's spent cartridge case used in the substitution exercise involving exchanging the original piece of a badly fragmented bullet which had been the original PV/20 exhibit!
It then becomes possible, should you wish to take this matter to its full conclusion, to say that there has been a total of 27 bullets fired in the effort to resolve the ballistics involved in this police investigation, as follows:-
Total number of shots fired at scene in the tragedy - 26
Total number of weapons used in shootings at the scene - 2
Total number of bullets recovered from the scene / bodies of victims 25
Total number of spent cartridge cases recovered from scene - 25
Total number of spent cartridge cases not officially recovered from the scene - 1
Total number of test fired rounds used in substitution of PV/20 - 1
Total number of test fired bullets used - 1
Total number of test fired spent cartridge cases - 1
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25 bullets (batch of crime scene Ammunition) + the original piece of a badly fragmented bullet used in the substitution procedure involving PV/20 + the unrecovered bullet from the skull of Nicholas Caffell = 27 bullets, where of the 26 shots that were fired at the scene were made up of, 25 which had been fired by way of let's say (1) domestic weapon (a), and shots fired by (2) domestic weapon (b), the ratio for which is irrelevant for the purpose of this explanation but which can be gone into elsewhere + a shot from a police issue weapon (the shot which was originally inflicted to Sheila's neck at the time of the raid teams entry into the kitchen..
Then there was the control round which had to be test fired post the tragedy, fired via (1) domestic weapon (a) - a total of 27 bullets, including the 25 bullets which were recovered from the scene + one bullet used in the substitution process involving the original PV/20 exhibit + the unrecovered bullet left in the skull of a child victim...
Two missing, unaccounted for spent cartridge cases, since although overall a total of 27 bullets fired, there has only been disclosure of 25 corresponding spent cartridge cases..