Week 3A - 4 Analysis of Skeletal Remains I

Loading...

Del curso dictado por Nanyang Technological University, Singapore

Introduction to Forensic Science

457 calificaciones

Nanyang Technological University, Singapore

Introduction to Forensic Science

457 calificaciones

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.

De la lección

Time of Death; Blood

Week 3A - 1 Recent Deaths10:39

Week 3A - 2 Decomposing Bodies I (Putrefaction)6:13

Week 3A - 3 Decomposing Bodies II (Forensic Entomology)11:50

Week 3A - 4 Analysis of Skeletal Remains I8:29

Week 3A - 5 Analysis of Skeletal Remains II11:37

Week 3A - 6 Ötzi Case; Summary3:36

Week 3B - 1 Blood13:02

Week 3B - 2 Tests for Blood6:54

Week 3B - 3 Precipitin Technology3:53

Week 3B - 4 Blood Spatter Analysis8:17

Week 3B - 5 Lord Lucan Case; Summary7:04

Conoce a los instructores

Roderick Bates
Associate Professor
Division of Chemistry & Biological Chemistry | School of Physical & Mathematical Sciences

[MUSIC]

Ultimately the body is going to turn into a skeleton.

And once it's a skeleton it's very difficult to get good information

because bones after all are bones.

One test that can be done is to look at fluorescence.

Fresh bone will fluoresce under UV light.

Old bone, maybe more than a hundred years old bone will no longer fluoresce.

And this is very useful because if bones turn out to be more than a hundred years

old, then you can be pretty safe in assuming that anyone associated

with that event is also going to be dead by this time.

You can do some analysis to get some more information.

What we can do is use techniques of elemental analysis to measure the level

of specific elements in the bone and this can enlighten us a little more.

This is typically called FUN analysis after three elements,

fluorine, uranium, and nitrogen.

Now fresh bone contains proteins.

All proteins contain the element nitrogen.

And in fresh bone, if you analyze it,

you will find that bone is about 4% nitrogen by weight.

However, let's suppose the body is in a grave or

somewhere, exposed.

The proteins in those bones will gradually break down with time.

But as the protein molecules break down, the nitrogen containing compounds will

diffuse out of the bone into the environment and be lost.

Which means that the bone nitrogen content will decrease with age.

Now, let's turn to the upper two elements, fluorine and uranium.

These two elements are not naturally present in bone, so

the content of these two elements in fresh bone is 0%.

There shouldn't be any fluorine or uranium in your bones.

Now suppose those bones are buried in an area where

the groundwater contains appreciable amounts of those elements,

okay, they would be leaked from the local rocks.

Then, the bones will absorb those elements from the environment.

And that means that the concentration of fluorine and

uranium will increase with time.

Now, you cannot use this as a kind of clock to determine time of death,

because the absorption of these elements depends on their presence

in the local environment.

So if that body is in a place where the local geochemistry means there is no

uranium, then of course it will not absorb any uranium however long you leave it.

But if it's in an area where there is uranium naturally present

as a trace mineral in the rocks, then you will get uranium absorption.

So you can't use it as a clock, but

you can use it to compare two bones from the same place.

And if those two bones have been in the same place for

the same length of time, the same number of centuries maybe,

then they should have the same amount of uranium and fluorine.

Here's an example where this kind of analysis proved critical, and

this is the story of Piltdown Man.

If we go back about 100 years or a little bit more,

one of the great scientific challenges was finding the ancestors,

our own ancestors, the ancestors of homosapiens.

Now the Germans had found the remains of ancient humanoids.

And this is Neanderthal Man.

The French have found the remains of ancient humanoids as well.

And this is Cro-Magnon Man.

And since then of course we also have Peking Man and Java Man.

And all the discoveries in East Africa.

But 100 years ago, British paleontologists were very disappointed because they had

not been able to find any ancient humanoid remains anywhere in Britain.

So they had nothing to compare with the remains found by the Germans and

the French.

Well, one dig that was going on was at a place called Piltdown.

It's a little way outside London.

And this was during the period 1912 to 1915.

And alongside many, many bones of prehistoric animals,

they also found two fragments of humanoid bone and

they claimed that these were approximately 500,000 years old.

And so of course they went to the Natural History Museum in London and

they were displayed in private place.

Now what they'd found was two fragments of bone, and

you can see the reconstruction in this picture here.

What they found is the two dark parts.

You can see a skull fragment, and you can see a jaw fragment.

When you look at these fragments,

you conclude that the skull fragment is very similar to a modern human.

Whereas the jaw fragment is more similar to a modern ape,

which indicates that in evolutionary terms,

our brain case evolved before our jaw evolved.

And this finding was never completely accepted by the community.

Because the more favorite theory was the jaw evolved in advance as the brain.

Nevertheless, both bone fragments were there in

the Natural History Museum until the late 1940s.

By the late 1940s, chemical techniques have improved a lot and someone had

the courage to go to these bone fragments and do a little bit of chemical analysis.

In fact, he analyzed them for fluorine and nitrogen, and this is what they found.

The skull fragment turned out to be 0.2% fluorine, whereas the jaw

fragment had essentially no detectable fluorine, or almost no fluorine.

That means that the two pieces of bone

had not been in that site at Piltdown until for

the same length of time, therefore they could not come from the same individual.

They had to come from different individuals.

What's more, the jaw fragment turned out to contain almost 4% nitrogen,

which meant that the jaw fragment must be essentially a modern piece of bone.

Well, it turned out that,

that jaw fragment actually have been taken from a modern orang-utan.

Whereas the skull fragment was human, and it was a few centuries old.

And it was a hoax.

Someone had acquired these two bone fragments, had chemically dyed them so

that they're the dark color that you see in the picture, and therefore look old.

And that person had placed them in the excavation, so

that they would be found by the paleontologists.

Well, it's never been proved who did it.

There are suspicions about who might have done it, but of course,

after this length of time, it's never been proved.

But Piltdown man stands as one of the most famous examples of a scientific fraud.

But it's a scientific fraud that's been exposed by chemical analysis.

Explora nuestro catálogo

Inscríbete de manera gratuita y obtén recomendaciones personalizadas, actualizaciones y ofertas.

Coursera brinda acceso universal a la mejor educación del mundo, al asociarse con las mejores universidades y organizaciones, para ofrecer cursos en línea.

© 2019 Coursera Inc. Todos los derechos reservados.

Descargar en la App Store

Consíguelo en Google Play