[MUSIC] So hair is made of protein. And hairs are quite likely to be found at crime scenes, particularly violent scenes where hair may have been pulled out forcibly. Now when you look at a hair, it's just a hair, but actually hairs are quite complicated. So this is what a hair looks like when it's, for instance, growing out of your head. The hair grows out of a root, which is inside the follicle. It's inside the follicle that it is nourished by blood from blood vessels. Then the hair grows out through the skin, but the hair is not a single item, it's actually made up of different components within the hair. Now, the growth of the hair. When hairs start growing they are inside the so called anagen phase. This is the growth phase and this can last some years. Now in a violent incident, if a hair in the anagen phase is pulled out, for instance, in a fight. Then typically it's ripped out with the root of the hair, and the root of the hair will contain DNA. And this is of course extremely useful for identifying whose hair it is. Well after a few years the hair stops growing, its growth slows and then stops. This is the catagen phase. It's a transitional phase after the anagen phase. Then when the growth has stopped and the root shrivels up, the hair can fall out. This is called the telogen phase. So hairs that naturally fall out in the telogen phase, and these of course are the hairs that collect in the drain of your bath tub, these are much less useful for forensic purposes because they don't contain very much DNA at all. So let's look at the structure of a hair. The outside of the hair is called the cuticle. And this often, for instance, looks scaly. But by inspection of the cuticle, it's possible to identify the species from which it came. Inside the cuticle is the cortex. And the cortex contains the pigment granules. So it's the cortex that controls your hair color. The pigment granules can be examined under a microscope, and you can determine the color and the size and the way they're distributed, and how closely they're packed in, and that's useful information. And in the very center is the medulla. And again, this is particularly useful for identification of the species. So here, for instance, are three different hairs. There's the cuticle, and you can see between human and dog and cat, they're quite different. Also the medulla, you can see the pattern for the human, the dog, and the cat hair are quite different. So from microscopic inspection, you can determine whether a hair is human or from a different animal. Now, how do we individualize a hair? In the ideal situation, there will be sufficient tissue from the follicle that you'll get enough DNA to identify whose hair it was, and this is typically true when that hair has been pulled out. If that is not the case, then it is necessary to rely on comparison. For instance, suppose you have a hair from a crime scene and a hair from a person, a suspect, or from a corpse, maybe the guy has been murdered. You can take the hair from the crime scene, the hair from the body or the person and you compare them under the microscope. This is not done by a scientific hair comparison machine. It is done by an experienced expert. So the judgment as to whether those two hairs come from the same head is the opinion of an expert. And like all human activities, it can be wrong. So for instance, in a survey done by the FBI, 11% were misassigned, so we cannot say that hair examination, in comparison, is particularly accurate. Now hair analysis also gives us another opportunity. We said in the first lecture that forensic science enables us to reconstruct what happens in the past. The hair, your hair, contains a record of the chemicals that were in your body in the past. If you consider hair growing out of your head, typically hairs grow at about half an inch, that's 1.25 centimeters per month. As the hair grows, it's nourished by those blood vessels, but any extraneous chemicals in your blood will also be deposited in the hair. As the hair grows out, those chemicals will be locked into the hair. For instance a bar, a disreputable bar, is raided by the police. The people in the bar are required to give urine samples. Someone is found to be positive for a drug. Let's say it's ketamine. They're questioned by the police and they deny that they're a ketamine user. And they say that maybe somebody slipped the stuff in their drink that evening. How can we find out whether they're telling the truth? You can do it by hair analysis. Take a hair sample, cut off at the scalp. At the scalp will be the newest hair, cut it into segments, analyze the segments. If that person's telling the truth, then there will be no ketamine in the hair. But if you find ketamine relatively evenly distributed along the hair, then it tells you that person is a habitual user, and they're lying. So hair analysis helps us determine and reconstruct the past in terms of a person's chemical exposure. In the case of ketamine, we're determining whether someone willingly exposed themselves to that chemical. It can also tell if someone was unknowingly exposed to a chemical. So, Robert Curley died in August 1991. And analysis of his body fluids showed high levels of the toxic element thallium. And thallium of course is an element that we'll meet again in a lecture on toxicology. Now, Curley had done kind of maintenance work, handyman work. And he had worked doing this kind of thing In a university chemistry laboratory. So obvious suspicion is that he was exposed to thallium in that chemistry lab, and sure enough, there was a bottle of a thallium chemical in that lab. But it didn't add up, because the other people working in the lab did not show any traces of thallium. So when his wife tried to sue that university, the case didn't go anywhere. Now, further investigation showed that it was not only Robert Curley who'd been exposed to thallium. But low levels of thallium were detected in his family members and most significantly in a Thermos flask that he'd used to take a drink with his lunch box. And interestingly, he was insured for $297,000. This adds up to a lot of suspicion, and his body was exhumed, and in order to reconstruct his past exposure to thallium, samples of hair were taken, and analyzed. His hair was long enough that they could work out his thallium history for the last ten months, okay. His oldest hairs, his longest hairs were ten months old. And it turns out he had been exposed to thallium over a period of nine months. So he'd actually been exposed to thallium even before he worked in that university chemistry lab. So there were low levels, sometimes zero levels of thallium along the length of this hair almost. And a relatively high dose just before he died. So with this evidence, his wife confessed, and she was convicted of his murder.
