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.
Week 1 - 2 What is Forensic Science?
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Del curso dictado por Nanyang Technological University, Singapore
Introduction to Forensic Science
349 calificaciones
De la lección
Introduction to Forensic Science
Conoce a los instructores
Roderick BatesAssociate Professor
Division of Chemistry & Biological Chemistry | School of Physical & Mathematical Sciences
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Now, in this course,
what is it we're trying to explain to you?
What is it that we want you to take away from this course?
It's basically summed up by this question, how did they know?
When you hear forensic scientists or prosecutors or police
officers saying they have very strong evidence that this act
was done by this person, at this time, in this
way, you should wonder to yourself, how do they know?
And usually, how they know is based upon forensic science.
So this course is about explaining to you some of
the science, the scientific principles, that lets them make these statements.
It's about the interpretation of the evidence.
The evidence is found at the crime scene.
The evidence itself is merely physical objects or physical measurements.
These have to be interpreted.
So it's how this evidence is interpreted by the forensic scientists.
But a very important part is not just the interpretation of the evidence, it's
understanding how that evidence can be trusted
and to what extent it can be trusted.
How reliable is the evidence?
When DNA evidence is presented in court, it's
presented with great reliability as if it's infallible.
And in general, DNA evidence has tremendous reliability
because of the scientific principles on which it's based.
Other forms of forensic evidence?
Well, frankly, some of them are definitely a bit iffy
and their reliability is low,
much lower than DNA evidence.
And in addition to this, we have to be aware of
what we can deduce from the evidence and what we cannot deduce.
As we'll see, forensic science is tremendously good at telling
us certain pieces of information which go into solving a crime.
But there are some aspects of a crime
which are beyond the power of forensic science.
So, we have to know our limits.
Now, what about science?
Why do we consider this Forensic Science?
And, we call it Forensic Science because it uses the philosophy of all of science.
The model of science that we more or less use these
days is based on that given to us by Isaac Newton.
And in the Newton idea of science, you have observations.
Observations may be of the natural world or observations of your crime
scene, or you do experiments and you have results from those experiments.
And you use those observations and experiments to come
up with a theory that gives you an explanation.
You then go back to make further observations
or further experiments which then test your theory.
If both further observations and experiments support your theory, great,
then you can go on for further experiments.
If those observations and experiments contradict
your theory, well, you've gotta go
back to the drawing board and come up with a new theory.
And you would continue around this cycle
of observation or experiment and theory, until you
conclude that your theory is pretty much
firmly demonstrated, and you have full confidence in
it.
Now for most scientists, once you reach that point, what you do is
you write a scientific paper or you give a presentation at a conference
and there's the end to the process.
For forensic scientists, the end to the process is somewhat different
because once you are confident in your theory that explains
your observations, you then have to present that theory in court.
You have to be an expert witness in court, and convince
the judge and/or the jury of the validity of your thesis.
And this means that if there is a mistake in your theory, if your theory
is invalid, if it's wrong, the consequences can be very serious indeed.
Because if your theory is wrong, you may be sending an innocent person to prison;
or if it's a country where there is capital punishment,
you may be sending an innocent person to their death.
And it is certainly true that this has happened,
and this can happen.
Let us say a little bit at this point about the legal system, in particular, the
legal system in countries where they use a system based on the English system.
So, the evidence that is presented in the court when someone has
been charged with a crime, comes from experts such as forensic scientists.
It may come from witnesses, it may come from the police officers.
This is presented in the court.
Some of it is presented by the prosecution
who are seeking to get the person convicted,
and some of it will be presented by the defense who are seeking to oppose it.
And the prosecution and the defense will maybe challenge each other's evidence,
and each trying to achieve their objective.
Now, the court is presided over by a judge.
Now, in many countries that base their legal system on England, the
decision of whether the person is guilty or not guilty is taken by the jury.
And the jury is essentially a committee
formed, usually somewhat at random, from local citizens.
And the history of the jury system goes back many, many centuries indeed.
The jury system is still used in the United
Kingdom, in Australia, in New Zealand, and in the United
States of America, and in many of these places
it's regarded as an absolute cornerstone of the legal system.
In other countries, including Singapore, the jury system has been abolished.
In those countries then, the decision of guilty or not guilty
will be taken by a judge or a panel of judges,
but the fundamental system is the same.
The prosecution and the defense each try to make
their case based on the evidence in the court.
Another inheritance from English law is the presumption of innocence.
If you are charged with a crime, if you are accused of a crime, the legal
system must assume you are innocent until you are proven guilty.
Essentially, there is a default setting and the default setting is innocent.
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This means that it is the job of the prosecution to prove guilt.
The defense does not have to prove innocence.
They simply have to essentially pick holes in
the prosecution's case so that they cannot prove guilt.
Now, any case presented by the prosecution, you
can raise any kind of doubt about their case.
But the law does not allow any kind of doubt,
it has the concept of reasonable doubt.
If the defense can raise reasonable doubts about what the prosecution
is saying, then the accused must be found not guilty.
This case is a very good example of this idea of reasonable doubt.
Felicia Lee had a boyfriend called Randone,
and they were living together.
On September the 11th, 2009, Randone made a 911 call to the Emergency
Services asking them to come to the house because Felicia Lee was dead.
Okay, they arrived, she was dead.
Her body was taken away, of course, for autopsy examination.
When her body was examined, they found in excess of 300
what are called blunt force trauma wounds.
Essentially, she had been kicked or beaten very,
very savagely, in the opinion of the medical examiners.
And this is why Randone was charged not just with her murder, but
they also added on the very unusual, and very rare, charge of torture.
She'd been tortured to death.
So the prosecution's case was quite simple.
Here's Lee, in the house, the only other person there is Randone.
He kicked her to cause these excess of 300 traumas
and then had killed her by smothering.
And it looks, at first glance, a pretty cut and dried case.
But when a body is taken away for
autopsy, the pathologist, the medical practitioner, will not
only examine the body for the things that
the police, the investigators think caused the death.
They will go through a whole series of standard tests
because they want to check whether it may be other possibilities.
One of the standard tests that's done is blood chemistry.
A blood sample is sent away for analysis
and Felicia Lee's blood was found to contain
a chemical called gamma-hydroxybutyrate, GHB, which is a drug.
And the defense used this fact to
provide reasonable doubt to undermine the prosecution's case.
They called in an expert witness,
an expert who had studied the effects of the drug GHB extensively,
and he testified in court that these 300 bruises on
her body could have been caused by her having a seizure induced by this drug.
And her death could also have been caused by the fact
that she has an overdose of this drug in her system.
Result, he was found not guilty.
Let's look at that result.
Did the defense prove that her death was caused by an overdose of the drug GHB?
No.
They didn't prove it, the point is, they don't need to prove it.
All they need to do is to suggest that it is a possibility
and show to the jury that it is a reasonable possibility.
That is what they succeeded in doing.
That is all they needed to do.
And Randone was found not guilty.
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