Court of Appeal Judgement: R v T [2010] EWCA Crim 2439
On 26th October 2010, in the Court of Appeal, Lord Justice Thomas and Mr Justices
Beatson and Kitchen delivered their judgement following an appeal against the conviction
of T for murder. One of the grounds for appeal was the way in which footwear evidence
was presented.
As not everyone will have had the opportunity to read their Lordships’ judgement I am
attempting to précis the document. I will quote the judgement as it appears; I am making
no attempt to interpret their Lordships’ meaning or comment on their decision.
The Evidence
Footwear marks were recovered by an experienced footwear examiner at the crime scene
and compared with shoes (trainers) from the appellant’s house.
His examination revealed
i) the type and configuration of the pattern (and hence size) of the trainers were the same
as the marks at the scene. The pattern type was common.
ii) The wear on the trainers was greater than that on the shoes that made the marks. This
could be due to additional use in the intervening period.
iii) Some of the marks had features which might have resulted from damage to the
trainers; the trainers from the appellant showed no such damage.
There were three explanations for this
a) the marks were the result of an artefact on the floor;
b) the particular features could have worn away;
c) the marks could have been caused by a small stone which had subsequently been
dislodged.
The overall conclusion was “ ..it is somewhat unlikely that the observed correspondence
would have been obtained as a result of mere coincidence had the recovered footwear not
made the marks in question. …..there is at this stage a moderate degree of scientific
evidence to support the view that the Nike trainers recovered from the appellant had made
the footwear marks.”
After the trial the scientific notes were examined by a scientist with ‘no experience
whatsoever in footwear mark comparison’ who noticed that a formula and values were set
out and that a Bayesian approach had been used but not explored at the trial.
This was then put before the Court of Appeal and explored.
It became clear then that there was no mention in the report of likelihood ratios, statistical
information or the formula even though they were in fact used; the conclusion was solely
expressed in terms of the verbal scale. Also that trial counsel was not made aware of any
use of statistics.
The scientist explained that he had bases his opinion on his experience and the formula
for calculating a likelihood ratio merely as a guide. He used very conservative figures to
produce likelihood ratios for the frequencies of the pattern (P) and size (C) and the
amount of wear (W) and damage (D) and that a database of 8,122 shoes had been used for
the calculation of P. He multiplied these four values together to arrive at the LR of 100.
This figure was very much more favourable to the appellant than the one which would
have resulted if a figure for P was based on the population as a whole. This would have
given a likelihood ratio of 26,400 or ‘very strong support’.
The Judges discussed the development of likelihood ratios in England and Wales and
compared and contrasted this to the practice in The Netherlands, New Zealand,
Switzerland, Australia and the USA. They pointed out that the evaluative approach is not
universally adopted within the UK.
Considerations
The Judges then addressed the issue of whether a footwear examiner, having concluded
that a mark could have been made by a defendant’s shoe, could express an evaluative
opinion on the probability that it was.
Their Lordships accepted that where a sufficiently reliable database was available, as in
the case of DNA, then a straight statistical model could properly be used. However as this
was not the case with footwear the examiner could not attempt to use a formula to
calculate probabilities. Furthermore the data used in this case is only available to
examiners from one organisation.
However they acknowledge that there might be times when an examiner could go further
to express a more evaluative opinion where the conclusion is that the mark “could have
been made” by the footwear but that no likelihood ratio or other mathematical formula
should be used in reaching that judgement. Where this is the case it should be made clear
that the view is based on experience and the word “scientific” should not be used.
They recommend that where an evaluative opinion is expressed factors that enable this,
including data, must be clearly set out so that the report can be considered at a pre-trial
hearing.
Conclusion
On the basis that i) the statistical evidence was inherently unreliable, ii) the jury had not
been told the basis on which the conclusion had been reached and iii) the process had not
been transparent, the conviction was unsafe. Their Lordships had no criticism of the
scientist who they agreed was following standard procedures.
However, they concluded:
“For the future strict compliance with the requirements of transparency (as discussed
above- my comment) should ensure that in each case where an expert provider of a
forensic opinion seeks to develop a new way of arriving at an opinion, that new way can
be examined in open court applying the ordinary principles for the admissibility of expert
evidence.
We think there is no need for any new process”
The appeal was allowed and the conviction quashed.
Throughout the judgement the Judges referred to papers (among others referring to
overseas) as follows:



“A Bayesian approach to interpreting footwear marks on forensic casework” by
Evett, Lambert and Buckleton
“Principles of Interpretation- application of the likelihood ratio in marks cases” by
Jackson, Champod and Evett
“Standards for the formulation of evaluative forensic science opinion” as
discussed by the Forensic Science Advisory Council in December 2008.
Also to
 Professor Ormerod on Adams [1996] Crim L R 898
 Professor Glanville Williams “The Mathematics of Proof” [1979] Crim L R 346350
 Professor Redmayne “Doubts and Burdens: DNA Evidence, probability and the
Courts” [1995] Crim L R 464
 Chapter 4 of “Expert Evidence and Criminal Justice, Phipson on Evidence, 17th
ed. (2010) para 34-36 to34-38.
 Roberts and Zuckerman’s Criminal Evidence p. 123-132.
They refer to cases of Adams, Reed and Reed, Weller, Henderson, Pendleton, Doheny,
Dennis Adams and George.
Full details of all these references can be found in the Judgement.
Additional evidence from the Forensic Science Regulator and two other scientists, expert
in footwear marks and case assessment and interpretation was also considered by their
Lordships.
Dr Ann Priston
President, Forensic Science Society