50 Australian Geographic
I
F IT SOUNDS LIKE SOMETHING out of a TV
show, that’s because it is. “What people saw on
the TV 10 years ago has now finally started
happening,” says superintendent Mark Sweeney, the
acting commander of the NSW Police Forensic
Services Group. “It’s been promised to us ever since
CSI came out, but forensics now really have changed
the way police think about solving a crime.”
The advances in DNA technology are responsible
for the majority of that change, he explains. From
those aforementioned 20 skin cells, scientists can now
isolate 21 different markers on a DNA strand from a
crime scene sample and compare this with a reference
sample from a person. If there is a match between
the two samples, it’s an extremely strong indication
that the person is the source of the DNA – the same
combination of those 21 markers could be expected
to be seen in less than one in 100 billion individuals.“Actually, that’s just the cut-off number we give,”
Sharon adds. “In reality, the actual numbers generated
are far larger. The most common DNA profile occurs
in [about] one in a quintillion individuals. When we
go to court now, they generally don’t challenge who
the DNA originates from. That science is solid. It’s
typically all about how their DNA got there.”
And the technology continues to be refined and
improved. Over the past year, the Lidcombe facility
has introduced an automated way of processing DNA
samples, run entirely by robots. This reduces the risk
of contamination and means that DNA can now be
analysed and reported back to police in just two days.
After those initial 48 hours, the DNA results are
compared with every entry on the National Crimi-
nal Identification DNA Database, in addition to that
of persons of interest, to see if they come up with a
match. If a link is found, police will have theOver the past year, the Lidcombe facility has
introduced an automated way of processing
DNA samples, run entirely by robots.
Closing in. Victoria Police
forensic investigators assess
the crime scene after two
men were shot dead on
Melbourne’s Lygon Street.ROBERT PREZIOSO / STRINGER / GETTY