Statistical probability anyone?

[John]

Arguing over the technicalities relating to DNA profiling is unnecessary and I don't intend doing so.

The COA accepted that seventeen of the twenty bands attributable to Sheila Caffell were detected in DNA from the internal swabbings. Random chance would have suggested thirteen common bands would be found and hence since there was significantly more than thirteen, it provided some support for the DNA of Sheila Caffell being in the moderator.

They also agreed with the evidence of the two scientists and concluded that the major component of the DNA on the baffles did originate from June Bamber.

497.  We, therefore, consider the matter on the basis that the conclusions to be drawn from the DNA evidence are:

         i) June Bamber's DNA was in the sound moderator at the time of the DNA examination;

         ii) Sheila Caffell's DNA may have been in the sound moderator but it was not possible to
             conclude one way or the other whether it was; and

         iii) there was evidence of DNA from at least one male.


It also accepted that there was every possibility that the silencer was contaminated at some stage after the killings.

505.   Mr Webster concluded at paragraph 102:

           "The CCRC, in their statement of reasons, more or less excluded the possibility of contamination.
            In my opinion, the Commission was wrong to do so."

506.   We have no doubt at all that if this evidence had been placed before a jury, they would have concluded,
           as we do, that in accordance with the emphasised part of Mr Webster's report quoted above, the DNA
           testing results were rendered completely "completely meaningless".


www.bailii.org/ew/cases/EWCA/Crim/2002/2912.html

[John]

John are you able to explain the presence of June's DNA in the silencer?

497. We, therefore, consider the matter on the basis that the conclusions to be drawn from the DNA evidence are:

i) June Bamber's DNA was in the sound moderator at the time of the DNA examination;

ii) Sheila Caffell's DNA may have been in the sound moderator but it was not possible to conclude one way or the other whether it was; and

iii) there was evidence of DNA from at least one male.

Sorry for not answering this before.  I have had an opportunity to go back over this thread today and review the background facts pertaining to the blood analyses and the DNA LCN profiling which was carried out some years after the trial.

Fact: A full DNA profile matching June Bamber was extracted from inside the silencer.  The logical reason for this had to be back spatter. 

June was shot seven times some of which would have been in quick succession and according to the distribution of the empty cartridges found on her bed and on the floor beside her, some at least must have been fired at point blank range.
Given those circumstances therefore the air would have been thick with blood molecules so it would not be unreasonable to suggest some made their way into the silencer due to back spatter.

Do you agree?

[Holly Goodhead]

Arguing over the technicalities relating to DNA profiling is unnecessary and I don't intend doing so.

The COA accepted that seventeen of the twenty bands attributable to Sheila Caffell were detected in DNA from the internal swabbings. Random chance would have suggested thirteen common bands would be found and hence since there was significantly more than thirteen, it provided some support for the DNA of Sheila Caffell being in the moderator.

They also agreed with the evidence of the two scientists and concluded that the major component of the DNA on the baffles did originate from June Bamber.

497.  We, therefore, consider the matter on the basis that the conclusions to be drawn from the DNA evidence are:

         i) June Bamber's DNA was in the sound moderator at the time of the DNA examination;

         ii) Sheila Caffell's DNA may have been in the sound moderator but it was not possible to
             conclude one way or the other whether it was; and

         iii) there was evidence of DNA from at least one male.


It also accepted that there was every possibility that the silencer was contaminated at some stage after the killings.

505.   Mr Webster concluded at paragraph 102:

           "The CCRC, in their statement of reasons, more or less excluded the possibility of contamination.
            In my opinion, the Commission was wrong to do so."

506.   We have no doubt at all that if this evidence had been placed before a jury, they would have concluded,
           as we do, that in accordance with the emphasised part of Mr Webster's report quoted above, the DNA
           testing results were rendered completely "completely meaningless".


www.bailii.org/ew/cases/EWCA/Crim/2002/2912.html

Apologies if my post sounded a bit rude I didn't intend it to.  The subject matter is a bit on the heavy side to say the least and as I was a bit pushed for time I didn't word it as well as I could have done.

[Holly Goodhead]

Sorry for not answering this before.  I have had an opportunity to go back over this thread today and review the background facts pertaining to the blood analyses and the DNA LCN profiling which was carried out some years after the trial.

Fact: A full DNA profile matching June Bamber was extracted from inside the silencer.  The logical reason for this had to be back spatter. 

June was shot seven times some of which would have been in quick succession and according to the distribution of the empty cartridges found on her bed and on the floor beside her, some at least must have been fired at point blank range.
Given those circumstances therefore the air would have been thick with blood molecules so it would not be unreasonable to suggest some made their way into the silencer due to back spatter.

Do you agree?

No.

My understanding (despite Scipio trying to convince me otherwise) is that back spatter/blow back is a rare phenomenon.  When it does occur it normally does so with a large calibre weapon and not only is blood sucked back into the weapon/silencer but also skin tissue.  As we know the weapon involved with the WHF tragedy was a small calibre (.22) rifle and no skin tissue was detected with the blood. 

As far as I know the defence expert used at trial, Major Mead, did not even establish if back spatter/blow back was possible with a .22.

As we know the blood evidence presented at trial was based on a flake of blood found in the silencer.  When this was analysed it was shown to correspond with SC's blood type/group, and also RB's, as follows:

Blood flake/SC/RB = A, EAP BA, AK1, HP2-1 

The blood expert at trial Mr Hayward said it was possible that the blood represented an intimate mix of more than one person's blood and there was a "remote possibility" that the blood may have come from a combination of June's and NB:

June = A, EAP BA, AK2-1, HP2-1

+

NB = O, BAP BA, AK1, HP2-1

=  A, EAP BA, AK1, HP2-1  = blood flake found in silencer

This was the defence's case at trial ie that SC used the silencer to shoot her parents and sons and returned the silencer to the gun cupboard before shooting herself.  And that the blood found in the silencer represented an intimate mix of NB's and June's.  IMO this  is just the stuff of la la land and requires too many "remote possibilities" for it to sound credible:

That back spatter occurred in the first place

That it occurred with a small calibre weapon

That there was no accompanying skin tissue

That June's blood blew back into the silencer - one contact wound possible although expert said "unlikely"

That NB's blood blew back into the silencer - no contact wounds or even close ie within 1mm or 2mm.

That June's and NB's blood not only blew back into the silencer but blew back into the silencer at exactly the same spot; it then became intimately mixed (although this may have happened when the flake was dissolved by FSS for testing)

That SC then returned the silencer to the gun cupboard and replaced it in a box in a bag behind a dart board.

The above doesn't sound credible to me and yet that's what Geoffrey Rivlin QC expected the jury to believe!

June's blood group was not detected as a stand-alone in the silencer.  Mr Fletcher the ballistics expert thought it "unlikely" that the shot June received between the eyes was a contact shot making back spatter/blow back even less likely.  None of the other shots were potentially contact shots.

If June's DNA was in the silencer then I think it was there as a result of contamination possibly from where the silencer was handled with her bloody nightdress by jurors, expert witnesses, court officials. 

I'll explain why I said "if" later but have to go now!  Hope I've whet your appetite and left you wanting to know more! 

Btw you made a post yesterday but before I could respond it was gone/removed.  Anyway it was about animal blood.  The flake found in the silencer most certainly was not animal blood so at least we agree on that!

[Holly Goodhead]

If...June's DNA was in the silencer...

As June's blood sample was destroyed it was not possible to do a direct comparison between her DNA and the major component of DNA found in the silencer.  A sample was taken from June's closing living relative, Pamela Boutflour.  Closely related relatives are statistically more likely to have shared DNA components than unrelated individuals and this enabled conclusions to be drawn.  The evidence showed it was about 3,500 times more likely that the major source of DNA was from a sister of Pamela Boutflour's than an unrelated female.  Both the DNA experts at the CoA hearing, Mr Clayton and Ms Tomlinson, assessed this as strong evidence that the major component was from June Bamber.

As June's blood sample was destroyed the appeal court judges concluded that the major component of DNA on the baffles originated from June. 

[Holly Goodhead]

"Samples obtained from Sheila Caffell's natural mother and from other sources enabled the scientists to say with confidence that the major component did not come from Sheila Caffell"

The above is from CoA doc.  I've always been intrigued about the "other sources"!?  I wonder if this was SC's birth father!?  It surely must have been otherwise the court would need to apply some statistical evaluation as to the likelihood as they did with Pamela Boutflour and June?  With SC the scientists and court appear to have been satisfied to rely on samples from SC's natural mother and other sources to say with confidence that the major component of DNA did not come from SC  &%+((£

[John]

To get back to your opening post Holly, I don't believe statistical probability can help us with this case and indeed should not be used as a measure of guilt in any event.  Fortunately, there is enough evidence for us to determine that Sheila was innocent of any crime and Jerry guilty.