All language subtitles for Expert Witness - S01E01 - Soil and Insects

When a serious crime is committed and
the police need all the help they can

there's one group of people they turn to
time after time.

The expert witnesses.

Expert witnesses are the golden thread
that runs through cases that every

conviction needs.

An extraordinary army of men and women
with the expertise to reveal the hidden

clues criminals have left behind.

There are so many.

important pieces of evidence, paint
evidence, glass, fibre evidence.

They search harder and look deeper using
the very latest techniques.

If I can work out how old those insects
are, that's going to give me the minimum

time since death.

This is the inside story of how science
helped solve some of the UK's most

complex cases.

It really was becoming the last throw of
the dice.

Nothing's going to bring her back, but
she'd had the justice that she rightly

deserved.

This is the story of the expert witness.

Today, we travel to Edinburgh to look at
the fascinating story behind one of

Scotland's longest -running
investigations, the World's End Murders.

They just had the...

Terrible misfortune to cross paths with
two evil, dangerous men.

And we go to Scamenden Moor near
Huddersfield to look at the science

finding the killer of Christopher Pratt.

I like to think that the forensic
entomology is providing one bit of a

evidence and it might often be the
missing one that finally solves the

Our first investigation is a rare one, a
double murder from 1977.

Back then, forensic science was still in
its infancy, and a lack of evidence

meant that for nearly 40 years, the
killer went free, until a modern -day

witness unlocked clues hidden in some
soil samples and helped convict the

murderer.

Aberdeen, 2013.

Lorna Dawson has been asked to help
solve one of the UK's longest -running

cases, the World's End Murders. Lorna
remembers the crime only too well.

I got a phone call from Lothian and
Borders Police and they said, we've got

cold case here and there's some solid
samples that were taken from one of the

victims in the World's End Murders.

Would you be able to look at it?

I said, yes, we'll have a look at them.
And I thought, goodness me, that's the

case that was in Edinburgh when I was a
student.

Edinburgh, 1977,

a city famous for its nightlife, when
suddenly two 17 -year -old friends,

Scott and Christine Eadie, were
discovered murdered after a night out at

city's famous World's End pub.

I had just moved to Edinburgh as a
student studying geography and geology

shocked us all. There was a real fear,
particularly amongst my peers. I noticed

that there's a couple of men joining the
company and these are strangers and

they're seen speaking to Helen and
Christine.

At 10 o 'clock the pub's closed and
everybody leaves.

So they're seen leaving, going down St
Mary's Street in the company of these

men.

That was the last witness sighting of
the two young women. Helen's brother,

Kevin, was 11 years old. He remembers
growing panic at home as the hours

with no word from his sister.

I remember waking up and there was still
a light on in the house, so I got up

and my mother was sitting downstairs,
wondering why

Helen didn't come home.

Come the next morning, obviously...

There was a lot of concern.

You just knew it wasn't right.

The following day, Helen and Christine's
families received the news they were

dreading. Their daughters' bodies had
been found.

Firth was Christine's.

A dog walker had been walking along the
tide line on the beach and saw what he

thought was a tailor's dummy lying on
the coast.

As they approached, they got closer,
they realised it wasn't Taylor's dummy,

was actually the body of Christine.

Lying on top of her coat in the middle
of a field.

We came from an environment where nobody
locked their doors, so we were a

trusting family.

Helen was a trusting girl.

The household was just distraught. I
mean, it blows a family apart.

Police quickly secured the crime scene
and began an extensive search of the

where Helen's body was found.

We were lucky in that the first response
from our crime laboratory, our forensic

laboratory, were scientists who were
practised in crime scene management.

That morning on the 16th of October, a
young South African scientist called

Lester Nibb, he attended at the scene
and so he took possession of the coat,

took possession of the gaggings and the
bindings.

But Lester Nibb went even further.

He recovered forensic evidence for which
police did not yet have the science to

crack, including soil samples from the
body and the crime scene.

He secured these samples in a proper way
and made sure that not only were they

preserved properly, but that there was a
clear record of everywhere they had

been. And this is absolutely critical.

In 1977, forensic science was still in
its infancy. It would be decades before

these samples could be effectively
analysed. You know that something very

important is here.

You just don't have the means or the wit
or the science to interpret it.

So what you must do is you must retain
it carefully and you must monitor the

developments of a forensic science until
such times as it gives up its secrets.

One piece of evidence frustrated
detectives more than any other.

That's Helen's coat. And this is the
lining, which was so absolutely crucial.

There was a large stain.

which we always presumed was the
murderer.

But in 1977, there was no way for
science to identify who that person was.

It was very difficult for the police to
work out in those times what happened.

And, of course, then there was no DNA
technology, so it was very difficult,

although they had samples.

There was none of these new methods that
are now available that could help the

investigation of that crime.

For nearly 30 years, the investigation
made little progress and Helen and

Christine's killer remained on the
loose. Then, in 2003, advances in DNA

analysis gave police the breakthrough
they had been waiting for.

What they did was they looked at the
stain and if you think about that stain

on Helen's coat, it's a bit like DNA
soup.

And what they managed to do was they
managed to pick the individual elements

of this soup and actually create not
one, but two male profiles and

a female profile.

The female profile obviously was Helen
Harcourt, the one male profile, and it

was not on any database whatsoever.

But the second male profile, we checked
that against the database and that came

up. It's Angus Robertson Sinclair.

Angus Sinclair was a convicted murderer,
already in prison for killing another

young woman.

It turned out the second DNA profile
belonged to his brother -in -law, Gordon

Hamilton. Hamilton had died in 1996.

But with compelling new DNA evidence,
Angus Sinclair could now be prosecuted

the murder of Helen Scott and Christine
Eadie.

Nothing was certain, however, and Tom
was worried he needed even more to

guarantee a conviction.

Now, we had built up a very compelling
circumstantial case surrounding

that strong case of DNA because we
always suspected that what Angus

would say was, yes, I may have met them
and we had consensual sex, but I didn't

kill them.

Sure enough, in court, Sinclair's
defence team did precisely that.

Sinclair claimed the women were alive
when he left them and he denied their

murder. Without more supporting
evidence, he was acquitted.

I remember speaking to someone and they
said, well, that's it.

I remember these words, that's it,
there's nothing you can do.

And I remember walking away from that
thinking...

Somebody can do something.

It would take another seven years of
scientific progress, but that somebody

would prove to be soil expert Lorna
Dawson.

In the intervening period between the
first trial and 2013, we had been

developing methodology to look at the
organic profile in soil.

So soils vary across the landscape, but
they also vary with depth.

Because soil can be geo -referenced, the
inorganic part can tell us about what

the underlying geology is, and that is
mapped, so we know where it has come

from.

Soil helps us answer the where question.

They tried to convict Angus Sinclair in
2007 using DNA evidence alone.

It wasn't enough.

Now the investigation team turns to
samples of soil gathered by Lester Nibb

the original investigation.

Think about building this picture. So
you've not only got the strong central

feature of the DNA, but you also have
the background to the picture.

And the background to the picture is how
Helen Scott got to that place.

You know, was she carried? Was she
dumped? Did she walk?

In 2007, Angus Sinclair's defence team
claimed Helen was still alive when he

left her.

They insisted someone else must have
killed her.

Now, brand -new soil analysis techniques
could prove otherwise.

So these are the traces.

This is one of the aggregates from Helen
Scott's feet, LD4.

So this led...

to the conclusion that she had likely
stood or walked not only in the wheat

field but also at the grass verge,
leading the prosecutors to conclude that

had indeed been alive at that time and
likely walked to her death.

This discovery would prove a major
breakthrough, especially when combined

new evidence from the tights used to
bind Helen.

Between 2007 and 2013, DNA evidence had
come on.

We could tell a lot more from the knots
and bindings.

When we undid the bindings, we found low
-copy samples of Angus Sinclair's DNA,

and we could show through expert
witnesses that these knots had not only

tied by him, but they'd been tied
tightly by him.

Lorna's soil evidence proved Helen had
walked to where she had been killed.

Meanwhile, the DNA from the bindings put
Sinclair with her body.

We needed evidence from experts like
Lorna so as to support the DNA case.

It was very important to build up that
sequence of events.

We could then show that she had not
wandered off, that she had been walked

the field to be...

to be killed, all building up that
compelling picture

which Angus Sinclair could not wriggle
out of.

The team now had enough to start a brand
-new prosecution.

The trial was scheduled for 2014.

As the date drew for the start of the
new trial, you're always going to have a

concern that...

you're not going to get the result, the
desired result, that's going to bring

justice.

Everything was hanging on the new
evidence.

Lona had just one chance to explain to
the jury what she had found.

An expert witness must not... People
don't realise the amount of work that

into an examination, an analysis,
evaluation, and interpreting that

and then presenting it in court.

Lorna's evidence not only helped
contradict Sinclair's account of what

for the jury, it also offered a
compelling account of Helen Scott's

moments.

You're describing a scene and you're
painting a picture for a jury. The jury

have got to get their heads round a
whole three -dimensional picture of what

exactly took place here.

So the fact that Lorna Dawson could say
this...

Poor girl who was murdered in this field
was actually walked in. It was hugely

compelling.

Angus Sinclair was found guilty and
sentenced to 37 years, symbolic of the

it had taken to reach a conviction.

We have waited 37 years for justice.

Today, that wait has ended.

We finally have justice for Helen and
Christine.

Angus Sinclair was one of the most evil,
dangerous

men to walk the face of the UK.

All that's lost.

And that's the bit that you start to
think about.

Of all the evidence gathered at the
scene of a crime, perhaps one of the

surprising are the tiny creatures who
act as silent witnesses to the events

unfolded. Insect life can help prove a
timeline right at the beginning of an

investigation when clues are thin on the
ground. And our next case shows just

how crucial that evidence can be.

The number one question that police ask
me is, How long has this body been dead?

Forensic entomology is providing one bit
of a jigsaw evidence and it might often

be the missing one that finally solves
the picture.

2009. The body of a 51 -year -old man
has been found by a jogger.

Police are called to the scene and
journalist Nick Britton is assigned to

the case.

Christopher Pratt's body was found after
he went missing, lying naked in

wasteland near Scamondon.

Christopher Pratt was a civil servant
and father of two from Grantham in

Lincolnshire. His body had been on the
moor for some time.

Why he had been left there was a
mystery.

To solve it, forensic investigators
needed to act as quickly as possible, as

retired detective Roy Lambert explains.

You only get one chance.

He's now frequently called on as an
expert witness to determine time of

numerous murder investigations.

I've been working as an expert witness
in the field of forensic entomology for

about 30 years now.

Establishing time of death is really
important. It sets the whole timescale

the investigation.

I like to think that the forensic
entomology is providing...

One bit of a jigsaw evidence and it
might often be the missing one that

solves the picture.

Martin's ability to determine time of
death is all down to the life cycle of

blowflies. When a body is left in the
open air, they're quickly attracted to

and they egg.

Larvae hatch from these eggs and it's
their rate of development that provides

Martin with vital clues.

The life cycles of all blowflies are
very similar, so egg to larva to puparia

adult fly, but the rates of development
can vary, so it's very important

to get the identification correct if you
want to get the timing right.

Martin began an analysis of the insects
found on Chris Pratt's body.

Just as important as their species was
the temperature around the body. This

affects how quickly the larvae grow.

Blueflies grow almost exponentially,
really rapidly, and so even subtle

differences in temperature are
important.

The difference between these is 27
degrees and these ones just 21 degrees.

Only 6 degrees, but they're much, much
bigger in the jar here. If you don't

into account temperature, then there's
no way you can tell how old the insects

are. In a way, unlike us, they don't
just...

age in days they age proportional to
heat as well so there's no way at all of

telling how old these maggots are by
just looking at them what you need to do

take into account the temperature data
without that there's no way that you can

provide a accurate estimate of their age

scamond

and moore has a microclimate very
different to the surrounding area In

prove how long Christopher Pratt had
been lying there, Martin needed to work

the temperatures at the scene where the
body was discovered.

Not surprisingly, there wasn't a
convenient weather station right by the

and so what we needed to do was try to
get estimates of what the actual scene

temperatures were. So a data logger was
placed there by the scenes of crime

officers.

So this is a typical data logger. They
record temperature.

and relative humidity.

Basically they enable you to put the
temperature recording device at the

where the body was found and you can
record for ideally something like 10

after the body was removed and then you
can relate the temperatures from the

data logger to those at a nearby weather
station for the same period.

What this allowed us to do is then
actually work out what temperatures the

insects were experiencing and how fast
they would develop.

While Martin continued his analysis, the
police investigation also made

progress. They discovered that
Christopher Pratt had been seen with a

Desmond Lee.

Desmond Lee's a very dangerous man.

And by the time he met Christopher
Pratt, he'd already served one life

for murder, having murdered his... The
biggest maggots were around about 11mm

long.

From the laboratory studies, although
they were somewhat limited, we had a

pretty good idea of how long it would
take for those larvae to develop to that

size at the temperatures that we found
at the scene.

And so we were able to determine when
those eggs were first laid on the body.

Martin's evidence showed Christopher
Pratt's body lay on the moor for over

days until it was discovered.

At last, detectives had a likely time of
death.

They now looked for CCTV from around
this time.

When they found footage of Chris
entering Desmond Lee's flat, they

in for questioning.

Once, if you're lucky, you've
established a time frame of when a

died, as an investigator, you can then
use that when you're going questioning

witnesses and suspects to find out where
they were during that period,

to establish either an alibi or they
haven't got an alibi.

Desmond Lee had no alibi. Under
questioning, he admitted Christopher had

his flat.

but claimed it was an accident.

His neck was broken, his voice box was
crushed during an extremely violent act.

Lee claimed he put Chris's remains on
the moors out of panic, yet detectives

could show that before he even moved the
body, Lee had sufficient nerve to use

Chris Pratt's credit cards for a
personal spending spree.

He paid off his mobile phone bill that
night.

The next day, bought a load of goods
from a supermarket.

He then went back to the flat, bundled
Christopher's body into his car and

it to wasteland and just dumped it.

The callousness to do that is truly
extraordinary.

April 2010, at Leeds Crown Court,
Desmond Lee stood trial for the murder

Christopher Pratt.

During the trial, the weight of evidence
stacked up and stacked up against

Desmond Lee.

Of course, we had CCTV footage of
Christopher Pratt entering Desmond's

flat. We have the forensic entomologist
saying that he had been in the field

for... pretty much the entire time since
he was last seen. We have Desmond Lee's

history. He's a convicted killer. And
all of these things added up and led to

the jury convicting unanimously Desmond
Lee of Christopher Pratt's murder.

The judge sentenced Desmond Lee to life
imprisonment.

In this case, like in all cases where
we're able to help the police

investigation, I'm just astonished how
callous some people can be.

Two very different cases there, but
reassuring to see how both were finally

solved by science and the tenacity of an
expert witness so that justice can

finally be delivered.