If it is Robert Boutflour's blood in the silencer (which I doubt it is) it would be more likely that he felt human blood would suffice to incriminate Jeremy and that was it. It matching Sheila's was an 8% chance that fell in his favour.
With regards to your other points here is some of Malcolm Fletchers cross examination you might find interesting.
"Q. Are you familiar with the work of Doctors Stephens and Allan?
A. There is an article actually which I have a copy of from one of the journals, yes.
Q. You are familiar with it?
A. I am familiar with it, yes.
Q. They are respectively the Chief Medical Examiner for the Coroners Office and Fellow in Forensic Pathology at San Francisco and Medical Examiner to the Coroners Office?
A. Yes sir.
Q. Respected authority?
A. Yes sir as far as I am aware.
Q. May I put to you a number of propositions and invite your observations on the propositions? Presumably you would agree with this proposition, that under certain circumstances blood droplets can be propelled backwards in a direction against the line of fire?
A. Yes sir.
Q. That is what is known as back-spattering?
A. Yes sir.
Q. That phenomenon is the most commonly seen in contact gun-shot wounds to the head?
A. Yes sir.
Q. To the contact wound or very close?
A. That is correct, yes.
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Q. How much is the emission pressure reduced by the moderator?
A. I have no idea.
Q. Have you not tested it?
A. I don't have the equipment and facilities to do that.
Q. Have you sought others to test it for you?
A. No sir.
Q. It is rather important isn't it?
A. You obviously consider it so.
Q. Do you not as an expert?
A. The amount of reduction there is would have some effect on the possibility of back-spatter, but I wouldn't call it significant.
Q. How do you know?
A. Experience.
Q. With a .22, a silencer and back-spattering?
A. And with seeing
Q. Is that right?
A. And with seeing a lot of other weapons and ammunition fired, and their effects.
Q. I want to know about the .22, the moderator and back-spattering.
A. I have seen the effect of .22 back-spattering occasionally. I would say occasionally and not very often.
Q. When did you last see that?
A. I can't remember.
Q. Try.
A. I cannot remember.
Q. 22, back-spattering, with a moderator, when have you seen that?
A. I can't recall having seen one before today.
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Q. May I recap for a moment?
A. Certainly.
Q. You have assented to the proposition that back-spattering can occur less commonly with wounds to the head.
A. Yes sir.
Q. Is that right?
A. Yes.
Q. That the .22 is the least likely candidate for a gun to produce back-spattering.
A. Yes
Q. Mr. Fletcher, you cannot, as an expert, consciously and reasonably assert, can you, that there was any more than a possibility of blood spattering from the wound on Sheila Caffell's neck?
A. A possibility certainly, and a good possibility.
Q. A possibility.
A. A good possibility.
Q. How pray do you account for the absence of back-spattering from the two wounds at the head of the unfortunate Nicholas who received wounds to his head, the commonest area from which one gets back-spattering?
A. I don't know that there was not any back-spattering. As far as I can see there is no evidence of it."
You have to remember that Malcolm Fletcher is under oath, he can't make stuff up just because he knows something similar happened a few years ago, maybe even 10 years ago, but he doesn't have the fine grained, specific details on him in that moment.
If he can't remember the specifics, then he can't be specific.
He would risk perjuring himself.
Malcolm Fletcher would have had many experiences in a court room, being cross examined, so he knows not to get into an argument with the defense counsel, or get tied up in knots trying to answer questions for which he wasn't able to research thoroughly beforehand.
He would have had no idea that he was going to be asked about cases from his professional past, of which there may be over a thousand going back many years. So the only choice in that situation is to say you can't remember, because that would be the truth.
It's quite clever from the defense counsel though, because it makes Malcom Fletcher look vague, even though he comes across as very assured in the work that he did in the case.
For the defense argument to hold any weight, there would have to be scientific research to say categorically that it would be impossible for back spatter to occur for a .22 rifle with a silencer attached. And back spatter from a .22 rifle with a silencer on must never have ever been observed in actual real world cases, ever.
If the above paragraph is true, then the defense would have a valid argument. But they never got any where near that technical requirement with the dialog that you have published.
What I see is the defense trying to sew seeds of doubt in the minds of the jury.
Nearly 40 years have passed since this dialog took place, and scientific proof that back spatter cannot happen for a .22 rifle with a silencer on should exist now, if this were in fact true.
