At 22:48 20/01/04 -0800, Roy Carr-Hill wrote (off-list - see below):
>Dear John
>I actually think it is unlikely that the defence would have called on any
>statistical expertise. Whilst probabilistic and statistical are used in
>civil cases (partly because the criterion of proof is the balance of
>probablities), it is much less frequent in criminal cases, where the
>criterion of proof is 'beyond reasonable doubt'. All the prosecution had
>to argue in these cases as that 1 in 76 million was so small that it was
>'beyond reasonable doubt' and the defence wouldn't have realised that was
>actually based on a 1 in 8,500 probability (and if they had, they might
>well have searched for some advice).
The criterion of proof ('balance of probabilities' or 'beyond reasonable
doubt') is not really the issue.
I honestly don't think that it matters whether or not the defence realised
how the '1 in 76 million' was derived. What they must have realised was
that this '1 in 76 million' (or whatever) figure produced by a prosecution
Expert Witness was very likely to be regarded (as it was!) by the jury as
'beyond reasonable doubt' - such that I would have expected any competent
defence to challenge that figure (or face almost certain conviction) and
find some Expert Witness of their own to support that challenge. They may
well not have gone to a Statistician in the first instance, but surely
should have 'ended up with' a Statistician or Epidemiologist when they
discovered (as presumably they would have done) that no paediatrician or
expert from any other discipline could confirm the figure in question?
A statement by an Expert Witness for the prosecution which is effectively
trying to say that there is only a 1 in 76 million chance that the
defendant is innocent must surely be questioned challenged by any defence team?
Since no-one else has yet commented on this point I made recently, I'm also
going to repeat that I'm intriqued to know why, even if the jury (and
Expert Witness) DID believe that there was only a 1 in 76 million chance
that the two cot deaths had arisen 'naturally', how they jumped from that
to the specific conclusion that the mother was guilty of murder. Why not
the father (if one was on the scene), or maybe even other family member or
friend?
>P.S. If you think this is useful could you please forward to the List -
>whilst I can receive messages at this address as I forward them from a
>subscribed account, I can't send them to the List as this account is not
>subscribed.
Done. This message, with the quotes of Roy's message, has been sent to the
list.
Kind Regards,
John
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