Hair and Fibers

John D Wright, Jane Singer

• Publisher: Routledge
• Year: 2015
• Edition: 1
• eBook ISBN:
  9781317469247
• Topic: Economics
• Subtopic: Labour Economics
• Index: Economics

This introductory text on labour economics covers topics such as: the shift in America from a manufacturing-based economy to a service economy; the changes in the economic conditions in the US; the implications of NAFTA and GATT; and the labour markets.

A sample of hair is carefully prepared for analysis in a forensic science laboratory. Special care is taken to avoid contamination.

chapter 1

What Hair and Fibers Reveal

The most common clues at a crime scene are hair and fibers. Examined by forensic scientists, these clues can prove guilt.

When a crime is committed, even a careful criminal tends to leave clues, especially when violence is involved. Placing a suspect at the scene of a crime is a key element in criminal investigation. Among these traces of evidence are blood, flakes of skin, fingerprints, footprints, car tracks, mud, dust, paint flecks, firearm residue, and plant fragments. The most frequently found and analyzed, however, are hairs and fibers. Those from the criminal are found at the crime scene, and those from the victim are taken away, unwittingly, by the guilty, which is why a suspect’s home and possessions must be carefully searched.

Hairs and fibers are most frequently found in cases of homicide, aggravated assaults, and sexual assaults, because these types of crimes normally involve a struggle or other personal contact of some sort. Other cases include burglary—for example, when a burglar’s shoes pick up carpet fibers, or the burglar leaves behind hair or clothing fibers when squeezing through a window or other opening. In hit-and-run incidents, forceful contact with an automobile leaves behind the victim’s hair and clothing fibers, or even a fabric impression, on parts of the vehicle such as the bumper or windshield.

A magnified section of hair shows its distinct scales and characteristics. Different racial groups can be identified through hair analysis.

The French forensic scientist Edmond Locard devised the idea that “every contact leaves a trace” in 1920, and this became known as the “Locard Exchange Principle.” Earlier, he also established the world’s first crime laboratory, in Lyon, France, in 1910. Two years later, he solved a difficult murder case of a woman who had been strangled. The woman’s boyfriend, Emile Gourbin, a bank clerk, seemed to have a perfect alibi, but Locard examined his fingernails and found minute scrapings of skin still containing the pink dust of the woman’s face powder. The revelation prompted Gourbin to confess.

From the time of Locard’s early success, the profession of forensic science has grown and spread across the world. Today, many crime labs are now famous, such as those run in the United States by the Federal Bureau of Investigation (FBI) and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).

Hairs and fibers can place a suspect at the scene of a crime, support witness statements, and connect different areas of the crime, such as the murder scene, a suspect’s home or car, and the place where the victim was hidden or buried. Forensic scientists have an expert and finely detailed understanding of how hairs and fibers are transferred from one person to another, from person to object, and from place to place. They also know what makes a certain type of match important to an investigation.

Hair

One of the characteristics of hair is that, as with the skeleton, it lasts long after the body has decayed (unless it was destroyed by fire or acid). Hair also retains evidence of poison, such as arsenic, and even reveals when doses were administered, because of the constant rate of hair growth—about 0.5 inch (1.3 centimeters) a month.

The basic morphology of human hair is the same for everyone, but differences can be found by microscopic forensic examinations. These differences include the arrangement, distribution, and appearance of characteristics. Forensic scientists have done extensive research on the characteristics of hair and how it can be used in criminal cases. As far back as 1899, hair helped bring criminals to justice. Francois Goron, head of the French Sûreté, the national police force of France (similar to the FBI), was able to identify a murder victim because of the body’s dyed hair, which led to the arrest of the killers. A few years earlier, hair identification was not as advanced. Goron had found hair clutched in a dead woman’s hand, but examiners could not even identify it as human.

Investigators generally consider hairs from the head to be of greater importance than those from the body. Longer hairs give the forensic scientist more characteristics to compare, and a greater variation along the length increases its usefulness as evidence. The value of hair as evidence also depends on its type and condition, as well as the number of hairs recovered.

However, even a single strand of hair can lead to a conviction. When, in 1958, in Edmundston, Canada, the father of sixteen-year-old Gaetane Bouchard found her stabbed to death, he questioned her former boyfriend, John Vollman. Police found flakes of paint from Vollman’s car in a parking area frequented by teenagers, as well as traces of her lipstick on a half-eaten chocolate bar in his car. The strongest evidence, however, was one hair clutched in the girl’s hand. For the first time, using a technique known as neutron activation analysis, investigators matched the hair to Vollman’s. The hair’s ratio of sulfur radiation to phosphorus (fos-for-us) was closer to his hair than hers. This evidence convinced the jury, and Vollman received the death sentence, later commuted to life imprisonment.

In 1990, in Telluride, Colorado, another single strand of hair helped investigators catch a murderer. When Eva Shoen was shot dead, police suspected her husband, Sam, but they had no evidence. Three years later, a man phoned police from Arizona to say his brother, Frank Marquis, was probably the murderer. Marquis had been in the town when the murder was committed but then made a 400-mile (644-kilometer) trip with a companion, who told police Marquis had tossed two bundles out of the car. After an extensive search, police found one bundle containing Marquis’ clothes, including a shirt with one hair on it. Forensic scientist Joseph Snyder said it closely matched a sample from Marquis, based on structure and color. When presented with this evidence, Marquis confessed, claiming the death occurred during a bungled burglary. He received twenty-four years in prison for manslaughter.

A murder victim lies covered with a tarpaulin. It is essential that police keep crime scene areas clear for evidence collection.

KEY FACTS

STRUCTURE OF HAIR

Hair grows out of the skin’s follicle. The hair itself consists of three parts: the root (bulb), shaft, and tip. The root contains DNA, which can be extracted for testing, as well as blood factors. Under the microscope, the shapes of human hairs indicate the body part they came from: head hairs are round, beard hairs are triangular, armpit hairs are oval, eyelashes and eyebrows are tapered, and body hair is oval or triangular with curls.

The central core of a hair is the medulla, but, normally, the hair from a human head either has no medulla or a fragmented one, though people of East Asian origin have a continuous medulla.

An animal’s medulla can have a complex structure. The cortex surrounding the medulla contains the pigment that determines the hair’s color. The cuticle (the outside sheath) has overlapping scales. By examining these scales, scientists can identify different types of animal hairs, such as cat hair that has been transferred from an attacker’s clothes to a victim.

Varieties of Hair

Hair is valuable to criminal investigators because of its natural variety among individuals. Differences exist among racial types: Caucasian hairs have evenly distributed pigment granules; Asian hair has a wider diameter and thicker cuticle; and African hair has large pigment granules. Examiners can tell if hair has been dyed, cut, or pulled out. Hair shed naturally has undamaged, club-shaped roots, while a hair forcibly removed shows damage to the root and may have skin tissue attached. Hair can also indicate age and sex, which is valuable in identifying victims, such as those involved in accidents.

Despite this, hair is seldom used as the only indication of guilt, because a hair match is not as exact as a fingerprint match. Lawyers tend to speak of probabilities regarding a match of samples found on a victim and suspect. The chance of using hair for identification is about the same as using the ABO blood group system.

However, hair can be used to rule out particular types of suspects. For example: if a hair identified as belonging to a white person is clutched by a murder victim, that would exclude black or Asian suspects. Hair is more reliable as a carrier of deoxyribonucleic (de-oxy-ribo-nu-kle-ic) acid, or DNA for short, which is recovered in live cell tissue from the root. In a recent study, the FBI found that 11 percent of hairs considered to be matches by visual inspection were proven not to be matches by DNA testing.

Investigators at the forensic laboratory of the Royal Canadian Mounted Police estimate that if they positively identify a hair as being from an individual’s head, the chances of it belonging to another person would be one in 4,500. Other studies have found that the chance of a hair from a victim being on a suspect ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Introduction
• Chapter 1 What Hair and Fibers Reveal
• Chapter 2 Collecting and Analyzing Hair
• Chapter 3 Criminal Cases Involving Hair
• Chapter 4 Collecting and Analyzing Fibers
• Chapter 5 Criminal Cases Involving Fibers
• Chapter 6 Advances in Trace Evidence
• Glossary
• Learn More about
• About the Author/Quoted Sources
• Index