The transcript you are reading is not the full summing up. It is only the part which applies to the questions from the jury. I don't think I've ever seen the full summing up.
If the jury were mistakenly of the belief that the blood in the silencer could only have been sheiia's on the basis of the tests why did they ask about the chances if it being an intimate mixture of Neville and June's? And, why would the judge say that the nature of the wound is consistent with Sheila's blood being in the silencer (which us perfectly correct) as opposed to saying that Sheila's blood is in the silencer.
As I've said before the normal level of public understanding in the 80's was that blood could not be differentiated sufficiently so as to determine exactly the person from whom it came. Rather, it could only be narrowed down to groups of people with the same type or types. I don't see anything wrong at all with this small extract of the total summing up. If you want to make the case that someone else bled into the silencer prior to the murders that's up to you, but I don't think it's going anywhere personally.
Lol still haven't mastered the quote splitting yet

I blame it on your instructions

Perhaps because they were not convinced of JB's guilt. Also I believe the jury understood that the results were exclusive to an individual. Or in the case of June and NB an intimate mix as a result of the way the tests were carried out ie blood drawn from different parts of the sample to carry out the ABO, PGM, EAP, AK and Hp tests. (See lower down).
To my mind the judge saying "that the nature of the wound is consistent with Sheila's blood being in the silencer" is misleading and ambigious. However my interpretation is not important. In order for courts of law to deliver justice it is important that the jury have all the facts and figures stated clearly, concisely and consistently. Imo this did not happen with regard to how the blood test/group results were communicated. There's no standard language used with clear definitions given. I find it muddled, misleading and ambiguous.
I would like to see:
Standard language/terminology used throughout the whole process.
A clear definition of what exactly the blood type/group results represented:
- % of population sharing blood type/group or some other numeric expression
- the fact that the test results do not prove conclusively that SC's blood was in silencer
The possibility of contamination from manufacture to FSS
Which relatives were tested and the results
The fact that RB's blood type/group matched the blood sample found in the silencer and Sheila's blood type/group
Page 1, 2nd para of summing up/questions from jury"We need to hear blood expert's evidence regarding the blood in the silencer, (a) a perfect match of Sheila's blood, (b) what was the chance of the blood group being June and Ralph's mixing together"
The Jury sound confused, very confused

"Perfect match"
CoA, P.151. vi) a)a) "The blood grouping analysis proved (on the particular facts of the case) that Sheila Caffell's blood was inside the moderator; and"...
You assert "normal level of public understanding in the 80's was about type/groups etc." I don't believe it is for anyone to assume the level of public understanding. In order for courts of law to deliver justice it is important that the jury has placed before them all the facts and figures stated clearly, concisely and consistently. Imo this did not happen with regard to how the blood test/group results were communicated. There's no standard language used with clear definitions given. I find it muddled, misleading and ambiguous.