Forensics For Dummies®, 2nd Edition
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Library of Congress Control Number: 2019940131
ISBN 978-1-119-60896-7 (pbk); ISBN 978-1-119-60898-1 (ebk); ISBN 978-1-119-60900-1 (ebk)
You probably purchased Forensics For Dummies, 2nd Edition, because you’re fascinated by the marriage of criminal justice and science. I wrote this book because I have a similar fascination. And you and I are not alone. Shows such as CSI: Crime Scene Investigation, CSI: Miami, and NCIS have dominated network television ratings for many years, attesting to the fact that millions of people agree that forensics is an interesting subject. Every criminal investigation you see on the news or read about in the newspaper, it seems, hinges on some bit of forensic evidence.
This book is designed to give you an understanding of the techniques and procedures used by forensic scientists. The next time you read or view a mystery story or hear a news report about a crime, you can turn to this book for the science underlying the story.
Forensics For Dummies, 2nd Edition, is an introduction to the field of forensic science, covering a broad range of forensic topics in a clear and concise fashion. I explain these often complex principles in plain English so that readers at all levels can gain a better understanding of forensic science. The book includes many examples of how these techniques are applied in real-life situations. In addition, I include case studies throughout the book to illustrate how forensic science has been used to solve famous cases.
If you know absolutely nothing about forensics, this book is an excellent starting point. If you’re familiar with many forensic topics, this book serves to refresh and expand your knowledge.
Note: The conventional language used by scientists is foreign to most people, so I hold scientific jargon to a minimum in this book. Still, as with other areas of science, the study of forensics can be dry and boring at times. To avoid painting such an arid landscape, I added practical examples of how each technique works, and I included many famous cases that relied on forensic science for their solutions. I also threw in a little humor to liven things up a bit. If my humor falls flat, remember, I’m a physician, not a stand-up comedian.
As I wrote this book, I made some assumptions about you and what your needs may be, including that
Like other For Dummies books, this one has icons in the margins to guide you through the information and help you zero in on what you want to know. The following paragraphs describe the icons and what they mean.
This icon indicates that I’m giving you a look behind the scenes of a forensic practice or area of investigation. I use it to point out in-depth discussions of these concepts.
I use many real-life stories to illustrate the points in this book. This icon sets off these tales of crimes past.
Sometimes, to give you a clearer picture of how a forensic practice came about, I provide the historical background or a note about a related instance from long ago.
I flag certain pieces of information with this icon to let you know something is particularly worth keeping in mind.
Forensics deals with plenty of mind-blowing information about such things as the human body, evidence, and crime itself. For those of you who want just the juicy facts, look for this icon.
This icon signals that I’m going to delve a little deeper than usual into a scientific or medical explanation. I don’t mean to suggest the information is too difficult to understand — just a little more detailed.
This book is bursting with content, but you can go online and find even more. Check out the book’s Cheat Sheet at www.dummies.com/cheatsheet/forensics for tips on what to do if you witness a crime, tools of the trade in crime scene investigation, and more. And you can find some handy bonus articles related to forensics at www.dummies.com/extras/forensics.
Forensics is a broad and diverse field that involves many areas of science and criminal investigation. In this book, you can find out about many but not all of its concerns. You may use this book as a reference and as a springboard for further investigation. The next time you see a news report, read a mystery novel, or watch a movie involving a crime, you can turn to this book to obtain a better understanding of the science behind the story.
Part 1
IN THIS PART …
Discover how forensic science works.
Find out who makes up the forensics team and what they do.
Figure out how to properly collect and protect evidence at a crime scene.
Understand the inner workings of a criminal mind.
Chapter 1
IN THIS CHAPTER
Defining forensic science and checking out its origins
Understanding why the principle of evidence exchange is important
Unveiling how forensic science is organized
Revealing what services a crime lab offers
Turn on the TV any night of the week, and you’ll find crime scene investigators, or criminalists, tracking down criminals, crime lab technicians evaluating evidence, and even forensic pathologists conducting autopsies on shows detailing cases real or imagined. I don’t think this newfound interest in all things forensic stems from some macabre fascination with death or a guilty enchantment with the criminal world. If you ask me, people simply are curious by nature and have a strong appetite for scientific knowledge. Remember everyone’s fascination with the space program not too many years ago? The cool tools and magical feats of forensic science, such as making fingerprints appear from nowhere, identifying suspects by their shoeprints, sniffing out a forger by the unique signature of a laser printer, and finding even the most obscure poisons, are proving equally fascinating.
In this chapter, you get your feet wet with the basic definitions and organizational elements of the field of forensic science. Most of the topics that I touch on here are explored further in the chapters that follow.
If you lived in ancient Rome, you’d head to the forum when you wanted to discuss the news of the day. The town forum was a community meeting place for merchants, politicians, scholars, and citizens that doubled as a center for public justice. Steal your neighbor’s toga, and the case would be tried at the forum.
The term forensic stems from the Latin word forum and applies to anything that relates to law. Forensic science, or criminalistics, is the application of scientific disciplines to the law.
The same tools and principles that drive scientific research in universities and identify cures in hospitals are used by forensic scientists to reveal how a victim died and, ideally, who was responsible. In the same way modern hospital laboratories employ professionals to deal with pathology (the study of diseases of the human body), toxicology (the study of drugs and poisons), and serology (the study of blood), modern forensic laboratories employ experts in forensic pathology, forensic toxicology, and forensic serology, all of whom use the principles and testing procedures of their medical specialties to help resolve legal issues and answer questions like
Not long ago identifying, capturing, and convicting criminals depended primarily upon eyewitnesses and confessions. The world was smaller, communities more closely knit, and the extent of travel basically only as far as you could walk. Whenever anyone witnessed a crime, he likely knew the perpetrator. Case closed.
Trains, planes, and automobiles changed all that. Criminals can now rapidly travel far and wide, and with this newfound mobility they are less and less likely to be recognized by an eyewitness. Besides, eyewitness evidence these days frequently is proven to be unreliable (see Chapter 3).
For law enforcement to keep pace with these changes, other techniques for identifying criminals had to be developed. Science came to the rescue with methods that depend less on eyewitnesses to identify perpetrators or at least link them to their victims or crime scenes. Fingerprinting (Chapter 5), firearms identification and gunshot residue analysis (Chapter 18), hair and fiber studies (Chapter 17), blood typing (Chapter 14), DNA analysis (Chapter 15), and many other scientific techniques now help solve crimes that would’ve remained unsolved in the past.
The marriage of science and law hasn’t been without its setbacks. Many scientific breakthroughs are viewed with suspicion, if not downright hostility, until they become widely accepted. And before a science can ever enter the courtroom, it must be widely accepted. It should come as no surprise that before forensic science could develop, science in general had to reach a certain level of maturity.
The development of modern forensic science parallels general advancements in science, particularly the physical and biological sciences. Take a look at how a few milestones in science pushed forensic science several steps forward:
You witness a burglar sneaking away from a store late at night. You call the police, and when they arrive, you identify the thief as someone you know. That person is arrested. However, fingerprints from the store’s broken window, cracked safe, and tools used to open the safe don’t match those of the person you’ve identified. Instead, they match the fingerprints of a known safecracker. What do you think police, prosecutors, and more importantly, the jury are going to believe? After all, it was dark and raining, you were 100 feet away, you caught only a glimpse of the thief, and you’d just left a bar where you’d had a couple of drinks with friends. The fingerprints, on the other hand, match those of a known thief in each and every detail, meaning they came from him and only him. Which bit of evidence, the fingerprints or your eyewitness account, is more reliable?
This scenario represents what forensic science does, or at least attempts to do. Each and every forensic technique that you discover in this book is designed to either identify perpetrators or connect them to the crime.
Properly identifying, collecting, documenting, and storing evidence are at the heart of the forensic services offered by virtually all law enforcement agencies, from village cops to major metropolitan police departments. They need the basic services in the list that follows to be able to investigate and solve crimes and to convict the criminals who commit them:
Tracking down trace evidence, checking the characteristics of bullets fired from a gun, examining the penmanship of a signature on an important document, and evaluating the swirling ridges of fingerprints under a microscope all are part of the physical side of forensic science.
Forensic science deals not only with physical evidence but also with biological evidence, which may take the form of a corpse, skeletal remains, drugs and poisons, teeth, bite marks, insects, and plant materials, to name a few. It also includes analysis of the criminal mind. Biological evidence is often what makes or breaks a case.
For example, an autopsy (postmortem examination of the body, which is discussed in Chapter 9) may reveal the nature and cause of any injuries, the presence of any poisons, and ultimately why and how the victim died. These findings alone may lead to the perpetrator. Blood and DNA analysis can positively identify suspects and link them to crimes. DNA and dental pattern records can be used to identify an unidentified corpse, and plant and insect evidence can reveal the time of death and link a suspect to the crime scene. Find out more about these sciences and the people who specialize in them in Chapter 2.
Although they use much of the same equipment and follow similar research procedures, forensics (crime) labs are quite different from medical (clinical) labs. The latter deal with the living by carrying out testing aimed at diagnosing and treating the sick. On the other hand, forensics labs are geared toward testing evidence with the hope of establishing links between a suspect and a crime.
The United States’s first forensic laboratory was established in 1923 by August Volmer in the Los Angeles Police Department. Shortly thereafter, the first private forensic lab was created in Chicago in 1929 as a result of the investigation of Chicago’s infamous St. Valentine’s Day Massacre (see the nearby sidebar). This case involved the expertise of Calvin Goddard, then America’s leading firearms identification expert, who was able to link the killings to Al “Scarface” Capone. Two businessmen who served on the coroner’s inquest jury were so impressed with Goddard and his scientific use of firearms identification that they funded the development of a crime lab at Northwestern University. The lab brought together the disciplines of firearms examination, blood analysis, fingerprinting, and trace evidence analysis and served as a prototype for other labs.
In 1932, Goddard helped the Federal Bureau of Investigation (FBI) establish a national forensics laboratory that offered virtually every forensic service known to law enforcement across the United States. It, too, served as a model for future state and local labs. Now many states have networks of regional and local labs that support law enforcement at all levels.
Scientific services offered by modern crime labs and medical examiners’ offices are varied and complex. The number of services supplied by a particular laboratory depends on its size and budget. State and regional labs may provide a wide array of services, whereas local labs may provide only basic testing. These smaller labs typically outsource more sophisticated testing to larger regional labs. In addition, the FBI’s National Crime Lab offers services to law enforcement throughout the country. Not only does the FBI lab perform virtually every type of test, it also possesses or has access to databases on everything from fingerprints and tire-track impressions to postage stamps.
Larger labs often feature separate departments for each discipline, while smaller labs tend to combine services, perhaps even relying on a single technician to do all the work. Obviously, in this circumstance, a great deal of the work must be sent to larger regional labs.
Common procedures conducted in a crime lab include
Crime-scene investigators are charged with finding, collecting, protecting, and transporting all types of evidence to the crime lab. Although each person or team may have different ways of doing things, typical equipment and supplies they take to the scene include the following:
Every contact you make with another person, place, or object results in an exchange of physical materials. If you own a pet, this material exchange is well known to you. Look at your clothes and you’re likely to see cat or dog hair clinging to the fabric — a pain in the behind if you want to keep your clothes looking sharp, but an incredible boon for forensic science. You may also find that you transfer these hairs to your car, your office, and any other place you frequent.
Known as the Locard Exchange Principle, after Dr. Edmond Locard, the French police officer who first noticed it, the exchange of materials is the basis of modern forensic investigation. Using this principle, forensic scientists can determine where a suspect has been by analyzing trace evidence (any small piece of evidence), such as fibers on clothing, hair in a car, or gunk on the soles of shoes.
As an example, say that you have two children and a cat. You run out to take care of some errands that include stopping at a furniture store, the laundry, and the house of a friend who has one child and a dog. From a forensic science standpoint, this sequence of events can provide a gold mine of information.
You leave behind a little bit of yourself at each stop, including
But that’s not all. You also pick up similar materials everywhere you go:
In short, by merely running errands, you become a walking trace evidence factory.
An examination of your clothes and shoes after the preceding expedition essentially provides a travelogue of your errands. If someone robbed your friend’s house that evening while your friend was away, criminalists would find your fingerprints, your hair (as well as that of your children and your cat), and fibers from the carpets in your house and car. They could place you at the scene of the crime.
Of course, you’d have an alibi (I hope) and a legitimate reason why your trace evidence was found at the scene. The thief would not be able to offer a legitimate reason for his trace evidence being at the scene, which means the presence of his prints, hair, and carpet fibers would need an explanation.
Placing a suspect at the scene of a crime is one of the basic functions of forensic science. The analysis of fingerprints, blood, DNA, fibers, dirt, plant materials, paint, glass, shoe and tire impressions, and indeed every test done by the crime lab, is performed to create an association between the perpetrator and the crime.
In many cases, the mere fact that a suspect can be placed at the scene is an indication of guilt. A fingerprint on the faceplate of a cracked bank vault, semen obtained from a rape victim, or paint from the fender of a car involved in a hit-and-run accident connects suspects to crime scenes where they have no innocent reason for being.