The Reaction is overwhelmingly positive to news that the first case
to be featured on the BBC's Crimewatch programme has been solved
after a DNA profile produced from evidence at the scene was linked
to a family member of the killer on the national database leading
the police to the defendant. Paul Stewart Hutchinson pleaded guilty
to the murder of 16-year-old Colette Aram and was sentenced to life
imprisonment with a minimum term of 25 years. The evidence against
him included a DNA match, fingerprint, opportunity and confession.
as will be explained in this seminar, a DNA ‘match’
on the National DNA database might be wrong but the evidence could
still be admissible in a criminal trial.
is a complex chemical found in cells of the human body carrying
genetic information (half from each parent) which determines a person’s
physical characteristics. The DNA of any individual is the same
in all their bodily fluids and tissues. Except for identical twins,
each person’s DNA is unique although the science has not developed
enough to every difference between every person so the science deals
with regions of DNA. This means that DNA profiling techniques can
be used to exclude someone as a donor of a particular sample but
it cannot prove identity. In most cases, the scientists can provide
a match probability dealing with whether a stain came from the suspect
or from another individual with the same STR profile so, for example
people who are related might share STR profiles so the match probability
statistic can be calculated with that in mind.
IS DNA EVIDENCE?
form of DNA analysis used to test samples in most criminal cases
is called STR (short tandem repeat) profiling. A DNA profile from
a body fluid stain (such as blood, semen or saliva) can be compared
with the DNA profile obtained from a reference sample of any person.
If the profiles are different, then that person is excluded as a
possible source of the DNA. If the profiles are the same, then that
person, together with anyone else who has the same DNA profile,
can be considered as a potential source of the DNA. The evidential
significance of a match can then be evaluated in relation to the
probability of obtaining such a match by chance.
ARE SAMPLES OBTAINED?
most cases a sample is obtained from a scene and compared to a sample
taken from a suspect. Where there is no known suspect, the comparison
is done with those existing samples held on the national DNA database
(persons previously arrested).
some cases, defendants will argue that their DNA should not have
been retained after arrest where no action was taken (See case of
S. AND MARPER v. THE UNITED KINGDOM (Applications nos. 30562/04
and 30566/04) JUDGMENT STRASBOURG 4 December 2008.
WHEN IS DNA EVIDENCE ADMISSIBLE?
is no doubt as to the probative value of a full profile DNA match
taken from a scene sample such as a condom or a duvet. This is generally
admissible evidence in the same way as fingerprint evidence.
recently as December 21 2009, the Court of Appeal decided that low
template DNA and partial profile DNA are also admissible in certain
first case was R v David Reed and Terrence Reed. On August 7 2007
David Reed and Terence Reed were convicted at Teesside Crown Court
for the murder of Peter Hoe by multiple stabbing. The evidence against
them was both motive and opportunity. Telephone and witness evidence
put them in the area at the time of the killing and there was a
relevant background to the incident. The defence case was one of
quantities of DNA in relation to each defendant were found on two
pieces of plastic from knife handles found near Peter Hoe’s
body. The components of the DNA had been revealed using the Low
Copy Number (LCN) process. They were not from blood or other identifiable
biological material, but simply cellular material that had been
transferred to the pieces of plastic. There was no real dispute
with a defence assertion that the cellular material could have been
transferred from another source but the prosecution expert thought
this unlikely. She gave evidence that in her opinion the DNA got
there by handling.
LCN process allows for the analysis of very low quantities of DNA.
A tiny sample is recovered and copied then each component seen is
given a number. It is as if a drop is turned into a pond then the
experts go fishing for components and try to agree which components
are present. Each dip might bring up a different component but the
ones that appear the most are components which, according to expert
opinion, can be included in the sample and, in some cases, given
a statistic as to how many other people might be likely to have
the same DNA. Even where such a statistic cannot be given, the Court
of Appeal said that such low quantities could be used to say that
the defendant was not excluded from the potential pool even though
it could not be said how many other people could be included.
second case was R v Neil Garmson. Neil Garmson was convicted at
Stafford Crown Court on August 20 2007 of kidnap, rape and sexual
assault which related to incidents that had occurred in April 2005
and March 2006.
2005, the complainant, and her partner had gone by car to a country
park, a man tapped on the window then got into the car and demanded
that he be driven to Newport. He ordered the partner out of the
car, forced the woman to drive to a layby where he raped her. Afterwards
she was ordered to drop him off in Newport. Garmson was identified
by DNA taken in the 2006 incident.
March 2006 a man forced himself into the back of a car in which
a young woman was sitting. In the front passenger seat was another
woman. The driver was a man. The perpetrator threatened them with
a knife, demanded money and directed the man where to drive. He
then sexually assaulted the woman in the back seat. Both women managed
to escape. The driver was ordered to drop the man at a particular
location. Garmson was subsequently identified by DNA taken from
the lip of the victim. The DNA was merely a few components (known
as a partial profile) but the Court of Appeal concluded it was admissible
as it was not the only evidence. The prosecution also relied on
the similarity of the attacks, fibres from the car which matched
a jumper recovered from Garmson’s home, his knowledge of the
area and that the drop off was near his mother’s house along
with relevant comments he made on arrest .
as has been described, the Court of Appeal's judgment allows for
low samples of DNA and partial profiles to be admissible in a criminal
trial even where the accuracy of the findings depends on expert
opinion and/ or there is a possibility of transfer.
in mind that running a part profile (some components but not all)
through the database can give a ‘match’ for those components
but if only a part profile is recovered from a crime scene it will
never be known if the remaining components match the DNA of the
analysis of a crime scene sample, even in relation to DNA, is not
necessarily an exact science. The admissibility of a complex mix
of DNA from more than one person was considered in R v Ishaq at
Leicester Crown Court in January 2010. This was a cold case gang
rape from 2000 where there was DNA evidence which could prove presence
but some of which was also consistent with transfer. In addition,
experts eventually agreed on the day of trial that the possibility
of a person other than the defendant being responsible could not
be excluded as the computer had given an indication of components
present in a partial profile, which had initially been discounted
by the Forensic Science Service (FSS). At least one of those components
was not in the profile taken from Mr. Ishaq in 2008 and could not
be attributed to others implicated or convicted suggesting someone
else with some corresponding DNA components could have been responsible
and not Mr Ishaq. He was acquitted.
IS THERE A MINIMUM LIMIT ON AN AMOUNT OF DNA ADMISSIBLE?
finding of DNA at a crime scene is a useful tool in proving the
identity of the offender particularly in serious sexual offences
and murder. In all of the above cases the defendants suggested they
had an alibi for the events. The DNA evidence was used to put them
at the scene and therefore to prove the commission of the crime.
However, as few as four components were used in relation to Garmson,
the possibility of transfer was accepted in the Reed case and Mr.
Ishaq’s case made it plain that the FSS experts will exclude
components which the computer indicates are present and which could
exonerate a suspect.
Whilst making it clear there should be other
evidence, the Court of Appeal put no limit on how few components
can be considered as useful.
ARE THE SAFEGUARDS?
given in R. v Alan James Doheny  1 Cr. App. R. 369
following procedures should be adopted where DNA evidence is involved:
1. The scientist should adduce the evidence of the DNA comparisons
between the crime stain and the defendant's sample together with
his calculations of the random occurrence ratio.
• 2. Whenever DNA evidence is to be adduced the Crown should
serve on the defence details as to how the calculations have been
carried out which are sufficient to enable the defence to scrutinise
the basis of the calculations.
• 3. The Forensic Science Service should make available to
a defence expert, if requested, the databases upon which the calculations
have been based.
• 4. Any issue of expert evidence should be identified and,
if possible, resolved before trial. This area should be explored
by the court in the pre-trial review.
• 5. In giving evidence the expert will explain to the jury
the nature of the matching DNA characteristics between the DNA in
the crime stain and the DNA in the defendant's blood sample.
• 6. The expert will, on the basis of empirical statistical
data, give the jury the random occurrence ratio— the frequency
with which the matching DNA characteristics are likely to be found
in the population at large.
• 7. Provided that the expert has the necessary data, it may
then be appropriate for him to indicate how many people with the
matching characteristics are likely to be found in the United Kingdom
or a more limited relevant sub-group, for instance, the Caucasian,
sexually active males in the Manchester area.
• 8. It is then for the jury to decide, having regard to all
the relevant evidence, whether they are sure that it was the defendant
who left the crime stain, or whether it is possible that it was
left by someone else with the same matching DNA characteristics.
• 9. The expert should not be asked his opinion on the likelihood
that it was the defendant who left the crime stain, nor when giving
evidence should he use terminology which may lead the jury to believe
that he is expressing such an opinion.
• 10. It is inappropriate for an expert to expound a statistical
approach to evaluating the likelihood that the defendant left the
crime stain, since unnecessary theory and complexity deflect the
jury from their proper task.
• 11. In the summing-up careful directions are required in
respect of any issues of expert evidence and guidance should be
given to avoid confusion caused by areas of expert evidence where
no real issue exists.
• 12. The judge should explain to the jury the relevance of
the random occurrence ratio in arriving at their verdict and draw
attention to the extraneous evidence which provides the context
which gives that ratio its significance, and to that which conflicts
with the conclusion that the defendant was responsible for the crime
• 13. In relation to the random occurrence ratio, a direction
along the following lines may be appropriate, tailored to the facts
of the particular case: “ Members of the jury, if you accept
the scientific evidence called by the Crown this indicates that
there are probably only four or five white males in the United Kingdom
from whom that semen stain could have come. The defendant is one
of them. If that is the position, the decision you have to reach,
on all the evidence, is whether you are sure that it was the defendant
who left that stain or whether it is possible that it was one of
that other small group of men who share the same DNA characteristics.”
IF EXPERTS DISAGREE AS TO THEIR FINDINGS?
depends on what is in dispute but if the outcome of a trial depends
exclusively or almost exclusively on a serious disagreement between
distinguished and reputable experts, arguably it will be unwise,
and therefore unsafe, to proceed.
the Court of Appeal has made it clear that much depends on the other
evidence in the case, in relation to mixed, partial or low DNA,
one can quickly see that there is a real danger of an incorrect
to whether a court will allow expert evidence to be given to a jury
in relation to any sample recovered and compared to the defendant,
this is a matter for judicial discretion. Whether juries will leap
to the wrong conclusion based on the admission of low or few DNA
components remains to be seen.
Author of The Sexual Offences Handbook