Statistical Evidence and the Courts—Recent Developments
| Date | 01 April 1998 |
| Author | Beverley Steventon |
| Published date | 01 April 1998 |
| DOI | 10.1177/002201839806200207 |
| Subject Matter | Article |
STATISTICAL EVIDENCE
AND
THE
COURTS-
RECENT DEVELOPMENTS
l1ever/ey Steventon*
Where an item
of
evidence in a case is presented in statistical terms it may
cause particular problems for the courts. The use
of
DNA
profiling
evidence, a highly discriminatory technique, has increased awareness of
the potential for fallacious reasoning with regard to statistical evidence
and the difficulty the jury may have in combining such evidence with the
other evidence in the case. These issues mean that it is essential that the
parties concerned present the evidence in a clear and logical manner.
However, dispute may arise in relation to precisely how this should be
accomplished and to what extent mathematical theory may be presented
to the jury without leading to undue confusion and usurping their
function.
Two cases which recently came before the Court of Appeal, RvAdams
(Dennis John) Jand RvDoheny (A/an James)
..
RvAdams (Gary Andrew),2
can be used to elucidate these problems.
Presenting the statistical value of an item of evidence to the court: Rv
Doheny
In both the case of Doheny, an appeal against conviction for rape and
buggery, and that
of
Gary Andrew Adams, an appeal against conviction
for buggery,
DNA
evidence formed a significant part of the prosecution
case and one common ground of appeal concerned the manner in which
the DNA evidence was presented to the jury.
In order to understand the judgment and its implications, it is necessary
to consider the way in which
DNA
evidence has been presented to the
courts and the relevant terminology. Since the first introduction of
DNA
evidence its evidential value has been presented statistically. Initially these
statistics were reported as an estimate of the relative frequency of the
profile in the appropriate population. If, for example, the expected
frequency of the profile was 1 per 10,000 members of the population, ie a
frequency of 0.0001, then that could be presented in terms such as '
...
the
chance of obaining this profile from an individual chosen at random is
1 in 10,000'. This is known as the match probability. However, increasingly
an alternative method of presentation has been used. This method is
*Coventry University.
)[1996]2 Cr App R 467; 61 JCL 170.
2[1997]
I Cr App R 369.
176
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