Violent crimes such as murder, although
rare, leave a lasting legacy. Someone loses their life, and their
family has to live with the loss for the rest of their lives. Rapes
and sexual assaults leave victims with mental scars which will last
longer than any physical damage.
Over the years many people have been brought to justice for crimes
like these – but not all of them. There are people walking
about in the early 21st century living apparently normal lives who
committed terrible crimes 15, 20 or more years ago. But the development
of PCR and its use by police forces around the world means that
some people who must have thought they had ‘got away with
it’ are now being brought to justice.
 Police
forces are looking back over old, unsolved cases, bringing out old
evidence of semen stains, blood stains, cigarette butts ... DNA
has proved to be a tough molecule which survives for years. PCR
means the smallest traces of DNA can be amplified to provide enough
for scientists to produce a DNA fingerprint.
The story of Helena Greenwood is just one example of the way old
crimes are now being solved by new technology. The story is made
all the more poignant by the fact that Helena was a well-respected
researcher into DNA technology herself.
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