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Week 1 - 3 Application of Forensic Science

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Week 1 - 3 Application of Forensic Science

We have all seen forensic scientists in TV shows, but how do they really work? What is the science behind their work? The course aims to explain the scientific principles and techniques behind the work of forensic scientists and will be illustrated with numerous case studies from Singapore and around the world. Some questions which we will attempt to address include: How did forensics come about? What is the role of forensics in police work? Can these methods be used in non-criminal areas? Blood. What is it? How can traces of blood be found and used in evidence? Is DNA chemistry really so powerful? What happens (biologically and chemically) if someone tries to poison me? What happens if I try to poison myself? How can we tell how long someone has been dead? What if they have been dead for a really long time? Can a little piece of a carpet fluff, or a single hair, convict someone? Was Emperor Napoleon murdered by the perfidious British, or killed by his wallpaper? *For Nanyang Technological University (NTU) students, please be noted that this course will no longer be eligible for credit transfer.

Impartido por:

Roderick Bates
Associate Professor

Transcripción

[MUSIC]

When forensic science is used in court, then the side, the prosecution or

the defense,

that's presenting that forensic evidence has to convince the judge or the jury,

depending on your system, of the validity of that forensic evidence.

Sometimes it's difficult to convince the court of the validity of

scientific evidence.

Especially because the members of the court, the judge and the jury,

will generally not have any scientific training themselves.

This case, which is from many years ago, 1939,

illustrates the difficulty of conveying scientific evidence in the courtroom.

So this is a case from the town of Bournemouth in England, back in 1939.

And it concerns a man, a fairly wealthy man called Walter Dinivan.

He was 64 years old, and he was found in his home unconscious.

And his head had been bashed so that his skull was crushed.

He was rushed to hospital, but he died there without regaining consciousness.

So in this crime there's immediately a problem for the investigators

in that there's only one witness to the crime, the victim, and he's dead.

The investigators therefore had to rely very heavily

on forensic evidence to try to prove their case.

Well, of course, the crime scene is searched and investigated carefully.

And the first thing that could be determined was the motive,

because Dinivan's valuables from his safe and from his pocket were gone.

It's clearly a robbery.

They also found a crumpled up brown paper bag.

And they suspected that the murderer had used this in order to hold

the murder weapon so that he wouldn't leave any fingerprints.

On the floor they found cigarette butts.

So the scenario that they pictured was the murderer and

Walter Dinivan had been talking, smoking cigarettes.

And the conversation had escalated into an argument,

into a fight, and this had led to murder.

In police work, forensic science is only one element of solving a case.

There are always inquiries made by police officers.

And the inquiries, in this case,

led the police to suspect a local man called Joseph Williams.

And from their inquiries, they knew that normally Joseph Williams

was a pretty hard up guy with not much money.

But suddenly, he'd come into money.

And they suspected that the money that was now flush in Joseph Williams' pockets

was the money from Walter Dinivan.

This was 1939, and a few years before, an interesting discovery had been made.

And scientists had discovered that you could determine

the blood group of a person from saliva.

Now it's not true for everyone, but for

a large percentage of the population you can do this.

If you have a sample of saliva, you can tell which blood group they are.

Remember that the police had the cigarette butts from the floor so

they were able to extract saliva from the cigarette butts, test the blood group.

And very luckily, they turned out to be the AB group,

which is a really quite rare group in the population.

The obvious question therefore is, what blood group was Joseph Williams?

Now Williams of course is not going to voluntarily give this information.

And not going to voluntarily give a blood sample because he knows that

it could lead to his prosecution.

The police officer in this case was a very smart man.

He knew Williams was someone who liked to drink.

So when he observed that Williams went into a pub, he followed him in and

offered to buy him some beer and then to buy him some more.

And then to buy him some more and gave him some cigarettes to smoke and

some more cigarettes to smoke.

So at the end of the evening, all the police had to do was to gather up

the glasses and to gather up the cigarette ends.

Send them off to the lab, collect the saliva off them,

and analyze the blood group.

And sure enough Williams was found to have the rare AB grouping.

So the police have a motive, and

they have reasonable evidence that links Williams to the crime scene.

So he was arrested, he was taken to court.

He was charged, and the police presented their evidence.

Now the defense counsel was a very clever man, and

he looked at all the evidence being presented by the police.

And he saw the weak point was the saliva.

And when he spoke in the court, he cast

scorn upon the idea that you can determine blood group from saliva.

Because after all, blood is blood, and saliva is just a fancy word for spit.

So it goes against common sense that you can tell blood group from a piece of spit.

And he was very persuasive, and the jury did not believe that forensic evidence.

And therefore, they returned a verdict of not guilty, and Williams walked free.

Now we happen to know that Williams was the murderer.

Because after he walked free, he went to celebrate,

got drunk, and told the whole story to a journalist.

The journalist, of course, couldn't publish the story because there were no

witnesses, and he would be sued for libel.

So the story only came out years later after Joseph Williams' death.

So you can see from this case study that persuading a jury of

the validity of complex scientific evidence can be difficult.

But maybe things have changed.

Let's fast forward to Singapore in 1996, and this lady

Madam Singh was discovered murdered, killed by being stabbed in the neck.

And just like in the Joseph Williams, Walter Dinivan case,

at the crime scene the police found cigarette butts.

Now 1996, the technology wasn't there to do much.

But the evidence was stored away.

And almost ten years later in 2005, the evidence was dug out of storage.

The saliva was extracted from the cigarette butts.

And this time it's not blood group, it's DNA.

DNA was extracted from the saliva, and

it was put in to the national DNA database and out popped this name of Kemat.

He turned out to be very easy to find because he was in the prison

at time already serving a sentence for other offenses.

2005, the court accepted the scientific evidence,

and Kemat was sentenced to an additional prison term for

the culpable homicide of Madam Singh.

So perhaps times have changed.

Perhaps now society is more accepting of scientific advances, and

presenting it in court may be a little easier than it used to be.

[BLANK

AUDIO]

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