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 7 - 7 Inorganic Poisons - Arsenic
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From the course by Nanyang Technological University, Singapore
Introduction to Forensic Science
360 ratings
From the lesson
Toxicology
Meet the Instructors
Roderick BatesAssociate Professor
Division of Chemistry & Biological Chemistry | School of Physical & Mathematical Sciences
[MUSIC]
Okay, let's turn our attention to inorganic poisons.
So inorganic poisons are based around particular elements which are toxic.
And this means that inorganic poisons are a little different to organic poisons.
Where as our body will get rid of organic materials
such as ethanol or caffeine by transforming them to other substances,
we know from Robert Boyle that elements may neither be created not destroyed.
So these elements will always be these elements.
So if someone is poisoned with one of these elements
such as arsenic, antimony, mercury or
thallium, that element will still be detectable in the body after death.
It will still be detectable in the body after burial, and
it will even be detectable in the ashes after cremation.
Now one of the most famous poisons of all time is arsenic.
And Arsenic is a good indication of what power cell source said, because arsenic
compounds used to be readily available in any pharmacy or drug store.
For instance, Fowler's solution could be bought and it was widely used as a tonic.
Arsenic was also used in a thing called flypaper.
In the old days, before we've had these spray cans for
killing flies, the way to deal with them was to hang up flypapers.
Now a flypaper was a strip of paper and it was coated in glue.
So if the fly came along and landed on the paper, it would get stuck in the glue.
But flypapers didn't contain ordinary glue,
this was glue that had been contaminated deliberately with arsenic.
So the glue would stick the fly and the arsenic would then kill it.
Now we always associate arsenic with poisoning, but
as Paracelsus said, the difference between the poison and the remedy is the dose.
And this arsenic trioxide, which has this bad reputation,
is actually now been approved for treatment of certain types of leukemia.
The drug trisenox can actually be used in this kind of treatment.
Now we normally associate arsenic trioxide with the Victorian era.
And it was so widely used as a poison that it actually was given
the nickname inheritance powder.
That is, if someone was expecting an inheritance from their husband or their
parents and was getting a little impatient and wanted to speed up the process,
then they might use some arsenic trioxide inheritance powder to do just that.
Because of the widespread use of arsenic poisoning,
the Victorians desperately needed a reliable,
credible method for doing analysis, and
this resulted in a Marsh Test for arsenic.
Now in forensic science,
most of the techniques that are used are borrowed from other branches of science.
The Marsh Test is interesting because it is one of the scientific methods
specifically designed for forensic purposes.
And it was developed by this man James Marsh
after a murder trial had collapsed because the chemists
could not convince the court of the validity of their analysis.
So Marsh developed this test, very reliable, and
it was used for many, many years.
Now of course it has been superseded by modern methods,
such as atomic absorption spectroscopy.
So the Marsh Test relies on a property of arsenic.
That if you take an arsenic containing sample and you heat it with a reducing
agent such as metallic zinc with some acid such as hydrochloric acid,
then the arsenic will be reduced to arsine, which is the arsenic trihydride.
Arsenic trihydride is a gas, so it will bubble out of the solution.
It then passes along the tube to where there is a second heater,
the little spirit lamp there.
That heat from that lamp will decompose the arsenic and
the arsine, and the arsenic will be deposited on the surface of the glass.
And a trained chemist can not only confirm the presence of arsenic,
but can also estimate the amount of arsenic from the degree of deposition.
Why this test works so well is because there were only
two elements in the periodic table that will behave in this way.
One of them is arsenic.
The other one is arsenic's near relative antimony.
But the stipend, the antimony trihydride that would be produced if it were present
has a different stability, it's less stable than arsine.
So once again, the trained chemist can tell the difference between
arsenic deposited on the glass and antimony deposited on the glass.
The Marsh Test proved very effective and completely credible in the courts.
Therefore, a very, very powerful weapon in the hands of the prosecution.
But if the prosecution got better, then the defense had to respond.
And one of the methods that the accused could defend themselves, even if
arsenic were detected in the body, was by using the so-called Styrian Defence.
Now Styria region, a mountainous region of southern Austria.
And this is back in Victorian times, or
more correctly speaking Franz Joseffian times, it was found that the Peasants
in Styria had the habit of eating arsenic, or eating arsenic trioxide.
And they were eating large doses every few days.
They might be eating 300 to 400 milligrams, which,
whereas the lethal doses about half that.
And some of them could eat almost a gram.
And this was actually done, some of these Peasants were taken to a medical
congress in Vienna and ate arsenic in front of an audience of medical doctors.
So there were two questions.
How did they do it?
How could they eat this much arsenic trioxide without dropping dead?
There were various theories.
One theory is that the solid arsenic trioxide only released
into the body very, very slowly, so it never built up to a high concentration.
The other possibility is that because these Peasants had been eating arsenic for
a long time, starting maybe at low doses going to a higher doses,
they had built up a tolerance that other people didn't have.
Then there was the question of why did they do it?
Well, apparently they said they did it to improve their health.
And the women also said they did it
because they wanted to improve their complexion.
Now one of the effects of arsenic on the human body is that it damages
blood vessels.
In fact this damaging of blood vessels
is the reason that arsenic trioxide has anticancer activity.
Now if you damage the blood vessels in your face,
in your cheeks, then your cheeks will becoming more red colored.
And back in the 19th century,
having a nice red colored rosy cheeks like that was considered to be very attractive.
Now as for the men, well, they gave the usual reason for eating this arsenic.
So here's an example of someone who tried to use the Styrian Defence.
And this was a lady called Florence Maybrick, and
this was a very high profile trial in the city of Liverpool back in 1889.
Now Florence Maybrick was charged with murdering her husband James.
There was a motive, her husband had been playing around,
he had a series of mistresses, so she had a motive for doing it.
So let's see how the Styrian Defence played out for Florence Maybrick.
So the prosecution made the accusation.
They had the evidence that she had purchased arsenic.
In fact they found a huge amount of arsenic in the house.
And they had evidence, they had witnesses that she had been soaking
flypapers in water to make what is effectively an arsenic soup.
So the question from the prosecution is Mrs.
Maybrick, you did this to murder your husband.
Is there any other reason?
Her response, she wanted this arsenic containing soup
because she wanted to use it as a cosmetic face wash.
The prosecution, we dug up your husbands body,
the Marsh Test shows that there is arsenic in your husband's body.
Defense, self-medication.
Fowler's solution, which contains arsenic was widely available in those days and
many people took it.
Nevertheless, Florence Maybrick was found guilty and was sentenced to hang.
But this trial was very controversial,
not least because of the behavior of the judge.
Now in those days there was no appeal, but
with a big controversy in the newspapers, her sentence of death was
commuted by the Home Secretary and she was sent to prison for 15 years.
After her release from prison, she moved to the United States.
She lived a very long life, finally dying only in 1941.
Well, arsenic poisoning is not restricted to the Victorian era.
This is a case from 2003 and it's an arsenic poisoning that
occurred in the state of Maine up in New England in the United States.
And it concerns a church and the church congregation.
And the congregation had got together and they chatted,
eating sandwiches and drinking coffee that had been prepared for them.
And then quite a few members of the congregation became ill.
Well, when food has been prepared for a group like this,
it probably just a case of food poisoning and it's going to go away.
But the next day, one of the members of the congregation,
this man called Walter Morrill died in hospital.
So of course when somebody dies, the investigation becomes very serious.
So the leftover food and coffee was carefully tested.
And chemical tests showed that there was arsenic in the brewed coffee.
There was no arsenic in the sugar, no arsenic in the water, and
no arsenic in the coffee powder itself, it was in the brewed coffee.
The autopsy on Walter Morrill revealed the presence of arsenic in his body.
And when the people who had become ill but
had not died they were also tested, their bodies also contained arsenic.
So what was the conclusion here?
The conclusion was that somebody had put arsenic
into the coffee therefore this is a case of deliberate poisoning.
A few days later,
police were called to the house of one of the members of the church.
A farmer called Daniel Bondeson, and he had committed suicide,
he had shot himself.
And this brought the case to a conclusion.
So it's believed that this man,
Bondeson, had deliberately added arsenic to the coffee.
He'd gone into the room where the coffee was waiting during the church service so
that nobody had seen him doing it.
Where had he got the arsenic from?
Well, in the old days certain arsenic
compounds were used as agricultural chemicals.
This is potato farming country, and in the old days arsenic has been used
as a defoliant for the potato plants, just to make it easier to dig up the potatoes.
So it's probably an old agricultural chemical.
What was the motive?
Well, Bondeson is dead, nobody will know for sure.
But possibly it was some dispute over the church management or
something like that and perhaps he'd only intended to make people ill but
by accident had given an overdose leading to the death of Walter Morrow.
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