Would they not have taken these blood samples anyway, to eliminate them?
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Why would Essex police wait until September 1985, to take blood samples from the relatives, regarding blood allegedly found in a silencer a month previously? Now that we know there were two silencers, and that the one found in the gun cupboard by Boutflour was not found there until around 10/11th September 1985, one cane see why police were asking for blood samples from the relatives by 19th September 1985? The silencer with the blood inside it, was not sent to the Lab' until about 26th September 1985, along with a request for the silencer to be checked for blood and fibers from a tampon? And so, within days of the silencer being found, Essex police requested that blood samples be obtained from the relatives so that the silencer and the blood found inside it, could be checked to see if the donor was one of the relatives?
Which, as it happens, turned out to bear the same blood group activity as Robert Boutflour...