¿ìè¶ÌÊÓƵ

FORENSIC laboratories across Europe agreed last year on standard techniques
by which to produce DNA profiles. The laboratories hope this will help to
ward off some of the criticisms levelled against their counterparts in the
US.

Police in Britain first used the technique of DNA profiling in 1985,
and the country now shares the lead, with Switzerland and Germany, for using
this technology in Europe. In adopting the technique, however, the various
laboratories had employed a wealth of analytical tools to produce their
DNA profiles. In October they agreed to use one standard restriction enzyme
to chop the DNA in samples into fragments, and agreed on two of the standard
chemical probes with which to identify the DNA in these fragments.

‘If you have a standard enzyme and agreement on two probes then you
have the major elements of a standard technology,’ says Brian Sheard, director
of the forensic science laboratory of Britain’s Metropolitan Police, and
a prime mover in last year’s attempt to bring some order into the production
of DNA profiles in Europe. ‘A DNA profile is as much a function of your
choice of technology as it is a function of the individuality of a blood
or semen sample.’

Sheard’s laboratory has produced profiles for more than 700 cases in
London alone. Most of these are used to decide whether there is a case to
bring to court.

‘During 1989, we were able to go back to police officers in 28 per cent
of cases and tell them that they had the wrong person in custody. In these
instances the suspect was released without question.’

In Europe, Sheard argues, the forensic laboratories that produce profiles
for court cases have adopted a far more rigorous approach to that used in
the US. He says Europe’s laboratories have introduced dozens of techniques
to protect themselves from accusations of dubious scientific validity. In
Britain, for example, laboratories operate their own internal controls:
each runs a known sample of DNA alongside each profile it produces. What
happened in the US, he says, ‘was that a new company without any experience
in forensic science, and a little naive about what can happen in court,
was caught out’.

Another positive step that Sheard would like Europe to consider is a
joint programme of quality control, perhaps along the lines of that already
in operation in Britain. The laboratories are subject to a series of quality
control procedures run by the Home Office’s central research and support
establishment at Aldermaston. Home Office scientists send out dummy samples
and cases without informing the laboratories. These controls test the laboratories’
procedures, whether they are getting their answers right and their turnaround
time.

The need for such collaboration is increasing, he says, as more and
more laboratories reach the stage where they are capable of producing DNA
profiles.

Sheard is frustrated with statisticians who quibble, he says, over small
questions of inexactitude: ‘Whether the odds you are dealing with are one
in 35 million or one in 1.5 million, the numbers are still very large, even
having taken account of every statisical nuance.’ He does believe, however,
that the forensic community shot itself in the foot by quoting very specific
numbers on the reliability of its DNA matches.

Nevertheless, Howard Cooke, of the Medical Research Council’s Human
Genetics Unit in Edinburgh, feels there is a need for formal guidelines.
He does not believe that any scientist can look at two patterns and say
‘this is a match’. In the US, laboratories have to abide by strict mathematical
rules under which fragments can be deemed to match.

In the US, Congress seems likely to introduce legislation stipulating
standard technical procedures for commercial companies and laboratories
producing profiles. Sheard does not see the value of introducing similar
legal constraints in Britain. ‘It would be a pity if people run to legislation,
because it can box you in as science and technology move on. The important
thing is to do the profiles right, rather than according to any absolute
scientific method.’ molecular biologist at the University of California,
Irvine.