I have some knowledge of firearms and I have been thinking about what possible innocent explanations there might be for the blood and DNA found on and in the .22 moderator.
I've so far come up with two (beyond the obvious that members of the family will have handled it and used it):
(i). contamination resultant from cleaning the moderator; and,
(ii). contamination resultant from 'shooting wet'.
(i). Cleaning the moderator
Cleaning the moderator may well explain the DNA finding.
It's worth mentioning that there are differences of opinion within the firearms community about the advisability of cleaning rifles and moderators at all, but I would say that a .22 rifle and moderator, while at the borderline in this respect, should be cleaned.
A moderator is cleaned in order to remove not just ordinary dirt, but also residues of carbon and lead, which are present due to, respectively, the combustion of the rifle and simply the firing of the bullets through the barrel and then the moderator itself. Some firearms experts believe that it is best to leave a small coating of carbon inside the barrel and moderator, as this improves accuracy and suppression respectively, but an excess build-up of carbon should be avoided.
You can clean a moderator and its components (if taken apart) with any non-corrosive solvent: even simple soapy water will do. You also need an intrusive implement with which to clean the moderator. Things like toothbrushes are ideal. It can be anything that will get inside the moderator and between the baffles.
(ii). 'Shooting Wet'
The so-called practice of 'shooting wet' may well explain the blood finding.
One of the methods that can be used to improve the effectiveness of a moderator is to add a little water to coat the inside. This is sometimes called 'shooting wet'. I wonder if at some point Jeremy or maybe Nevill, or perhaps one of the cousins or nephews, has used the moderator in that way and it so happens that the water has been contaminated with human blood?
I realise that in a way, this is just shifting the goalposts, because you are then left to explain how the blood got into the water, but that could happen if the water is taken from a contaminated source containing clotted blood, such as a bucket or vestibule or container that contains clothing or anything else that has come into human contact.
Further questions
To develop this theme further, we'd need to know what the practices were at White House Farm for things like cleaning clothes, cleaning firearms and related equipment, general hygiene practices and even how the water and drainage system worked and whether there might have been the potential for routine contamination. I realise we're dealing here with a farm, which is quite old and owned and operated by an elderly couple.
