bar code that makes you who you are the
thing that makes everybody completely
different from everybody else when I was
doing biology a level in the 70s we were
told that one day we might be able to
read DNA and one day it might be able to
help us identify people from each other
well we can do that now your DNA is a
little bit like a ladder a ladder with
33 million rungs and if you were every
single one of those runs into a bag and
jumbled them up take them out one at a
time and put them on your ladder either
way round and then do it again that’s
the amount of different ways that each
person is built up so the odds of two
people having the same DNA or
infinitesimal except for identical twins
now in the 80s it was the first time
that DNA identification was used in a
legal case a boy from Ghana had come and
emigrated with his mother and his
siblings to the UK and he went home for
a visit when he came back again the
authorities thought that there was
something wrong with his passport and he
wasn’t the same person that went out
there and they tried to say that he was
trying to come in under a false passport
and that he wasn’t the son of the mother
who said he was well a woman from an
immigration charity called Sheena York
said actually I think there’s a
professor I’ve heard of that might be
able to do something about this and he
said no no we haven’t really got that
far with DNA yet but he worked on it and
he looked at it and he looked at the DNA
of the mother and he looked at the DNA
of the siblings and he matched the two
mixes up and said yes there’s no doubt
at all this child belongs to this mother
so therefore it was proved that he
should be in this country and he was
allowed to stay other cases for example
Richard the third when he was found in a
car park in Leicester which at the
moment is slightly more famous for
something else they would they were
pretty sure that the sky
it was old and they were pretty sure it
was the same formation as perhaps
Richard the third but by checking out
his siblings and looking at people that
were related to rich of the third they
said yep we definitely have found the
skeleton of a king in a car park and
he’s been reinterred in Leicester
Cathedral it’s also been used more
recently in a cold case where a rape and
murder in 1985 I think hadn’t been sold
and only recently the daughter of the
killer who kept quiet all those years
was taken into custody for something
else gave a DNA sample the sample was
checked on the database and it matched
this guy who they then arrested and
locked up for the murder that he
committed all those years ago and of
pick and we know that it solves cases
but how much DNA do we need what do we
know about the amount of DNA that’s
needed well actually it’s not very much
one DNA strand which gives you a full
sample to identify you is one nanometer
big and to let you know how big a
nanometer is there are 60,000 nanometers
for the width of a human hair so the
amount of DNA that is needed to identify
you he’s pretty small so if i was
thinking of committing a crime and I
didn’t want to pass my DNA on and get my
DNA on say a gun or a knife or something
then the sensible thing to do would be
to put a pair of gloves on so that if I
picked up this weapon for example it
wouldn’t have my DNA on it now if you
could pass me that bottle of water
please Ingrid if you just pass that
bottle of water forward
now my DNA’s not on this rock bottle of
water because I’ve got gloves on /
Ingrid’s DNA’s on it and Ingrid’s DNA is
now my gloves and Ingrid’s DNA is now on
this candlestick and that’s how easy it
is to pass d annoyed DNA on in a
secondary fashion so if that I’ve been
used to kill somebody my DNA isn’t on it
but few people here who touched that
bottle of water which I haven’t touched
with my hands the DNA has been passed
over onto a weapon and also if you went
shopping you went picked up something
like bottle of shampoo or something and
thought now that’s not the one for me
and put it back down again and then
somebody else pick that bottle of
shampoo up took it home touch something
in their house their your DNA is then
moved somewhere completely different to
somewhere you’ve never been and to
illustrate that I’ll tell you a story a
guy called Wesley decided he wanted to
buy a car he’d seen a car in the local
area that was for sale a couple of lads
that he knew was selling this Volvo so
he said can I give it a test drive and
they said yep so insured himself on it
for the day I wanted to give it a good
run round so obviously as he’s sitting
in this car he’s driving it about had it
for a few hours he didn’t actually
decide you wanted it so he took it back
back to these brothers two or three days
later this car was used in a drive-by
shooting and a 20 something year old
father was shot as he was riding his
to again later on has the police are
investigating they found the car had
been burnt out and there was one link
back to Wesley and that was that he
ensured himself on that car not only
that there was phone call on his phone
that took him back to the brothers that
were selling the car and when they
investigated in the house and found a
couple of balaclavas and a pair of
gloves where’s these DNA was on the
gloves where they hadn’t been in worn
those gloves whereas they hadn’t been in
the car when the shooting occurred but
the guys who were wearing those gloves
had held on to the steering wheel and
the gear stick so Wesley’s DNA had
transferred them to those gloves and to
cut a long story short although he had a
watertight alibi which of course the
police weren’t going to believe because
his DNA was on the gloves and he did
know these brothers DNA was he’s now
doing 27 years for murder so it’s a
cautionary tale and to be fair that sort
of thing doesn’t happen that often but
the point is that if we are going to be
using one nanometer of DNA to identify
somebody when it can be moved into
somewhere else as easily as that
everywhere you go DNA is passed
everything you touch your passing a DNA
on if you pick up one of those Bibles in
the pews in front of you you’re getting
somebody else’s DNA on your hands which
you could take home if someone drives
your car and then you drive it and go
somewhere else in the country a friend
of ours off and burrows our car so her
DNA could be in our cottage in Cornwall
because she’s past had a DNA it’s just a
case of maybe we should be looking at
larger DNA samples when we’re looking
for who they belonged to and where they
were at the time that it was passed on to something thank