LEVELED READER • XSeeing the Evidence: Forensic Scientists at Work Seeing the Evidence: A Reading A–Z Level X Leveled Reader Forensic Scientists at Work Word Count: 1,680 Written by Ron Fridell Visit www.readinga-z.com www.readinga-z.com for thousands of books and materials.
Introduction A man walks quickly across a ﬁeld into an old mill, a building where wheat is crushed to make ﬂour. Inside the building, he murders someone and then hurries away without being seen. Later, when police questioned the man, he insisted he was innocent. This suspect might have gotten away with murder if only he had wiped trace evidence off his shoes. Trace evidence is dust, hairs, threads, and other tiny bits of material found on or near a suspect or victim of a crime. When a detective named Edmond Table of Contents Locard used a microscope to study the man’s shoes, he noticed somethingIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 no one else had seen: traces of ﬂourCase File #1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 on the heels and soles. This trace evidence matched the ﬂour foundCase File #2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 at the mill where the victimCase File #3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 was murdered. This placed the man at the scene of theCase File #4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 crime and helped to convictConclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 him of murder.Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Traces of ﬂour, right, could be seen on the suspect’s shoes with a microscope, left. 3 4
The ﬂour mill murderer was caught by Besides these tools offorensic science, the use of science to solve crimes science, Holmesand convict criminals in courts of law. Detectives used his powers ofbegan to use science to solve crimes around concentration and1900. Before then, police used eyewitnesses and deduction to seeinformers to solve crimes. what no one else noticed. In A Case of Identity, for example, Victorian Holmes and boots, such his friend, as those from A Case of Identity Dr. Watson, receive a visit from a young lady who seeks their help in solving a crime. Holmes comments that she must have left home in a hurry, since her boots were mismatched and not properly laced up. Holmes’s deduction amazes Watson. Watson wonders how he missed this detail about their One of the ﬁrst detectives to use forensic visitor. It’s simple, Holmes says, “You did notscience was a make-believe one, an Englishman know where to look, and so you missed all thatnamed Sherlock Holmes. The popular Holmes was important.”stories and novels, written by Sir Arthur ConanDoyle, started appearing in 1887. Most of the In the following four real cases, forensicstories began in the ﬁctional detective’s cluttered scientists, like Holmes, know where to lookLondon home, where shelves bulged with to spot important evidence. As you read, putscientiﬁc reference books, and tables teemed with yourself in their place and test your own powerstest tubes and microscopes. of concentration and deduction. 5 6
How the Case Was Solved Case File #1 Place: Oregon, U.S.A. The police asked for help from Edward Date: October 11, 1923 Heinrich, head of the Berkeley, California, Crime: attempted robbery forensic science laboratory. Heinrich was famous of a train known as for being able to discover a great deal from very the “Gold Special” little evidence. Evidence: a pair of men’s overalls Heinrich told the police to be on the lookout for a left-The Crime handed lumberjack in his early twenties The scene of the crime is a weighing about 166remote stretch of railroad track pounds and standingin southern Oregon. The year is 5-feet, 10-inches1923. A Union Paciﬁc freight train tall. He also said thehas been robbed. The bandits lumberjack had lightkilled the engineer and used a brown hair, rolledhomemade dynamite bomb to blow open the mail his own cigarettes,car. Back then mail often held valuable stock and and was unusuallybond certiﬁcates and sometimes cash or gold. Edward Heinrich works in his neat about hisWhen police searched the scene, the only piece of Berkeley crime lab. appearance.evidence they found was a pair of stained overallsthat one of the bandits had left behind. C ase Fact! The bandits actually used too much dynamite and What could someone discover about blew up any money that may have been in the mail car. you from examining your clothing? The explosion was so loud and destructive they ran from What would it tell about you? the scene without having robbed anyone of anything. 7 8
right pocket left pocket And one more thing, Heinrich said, showing police a piece of paper he had found rolled up at the bottom corner of a pocket. more The paper was bleached clean wear from many washings, but when treated with iodine, words began to appear. It was a receipt from more fraying a post ofﬁce, made out to Roy Post Ofﬁce receipt D’Autremont of Eugene, Oregon. Police went to Roy’s house and learned that he was missing, along with his two brothers. Just as Holmes amazed Dr. Watson, Heinrich Neighbors’ descriptions of Roy matched Heinrich’samazed the police. How could he have description exactly. When police tracked downdiscovered all that from a pair of overalls? the brothers several years later, they confessed to the robbery and murder and were sent to prison. Heinrich explained: The fact that the left The railroad robbers case was just one of somepocket was more worn than the right meant the 2,000 cases that Heinrich solved during his careerowner was left-handed. What stained the overalls as a forensic investigator.was sap from trees that grow in southern Oregonforests where lumberjacks work. The overalls’ size told Heinrich thelumberjack’s height and weight, and Tobaccohe could estimate the owner’s age from strandsa light brown hair caught on a button. Tobacco shreds in a pocket Single and nail clippings caught in hair Nail a seam told him the rest. clippings Hugh D’Autremont Roy D’Autremont Ray D’Autremont 9 10
How the Case Was Solved Case File #2 Place: Anyplace U.S.A. How could the police discover their identities? Date: Anytime after 1950 The secret was on the thieves’ hands. Look closely Crime: a series of burglaries at the tips of your ﬁngers and thumbs, and you Evidence: dirty dishes will see raised ridges of skin running in patterns of curving lines: your ﬁngerprints. Each of your ﬁngerprints is different from the other nine, andThe Crime each one is unique. No one else on Earth has ﬁngerprints like yours, and no one ever will. Police believed that aseries of burglaries had In 1896, anbeen committed by the Englishmansame gang of thieves. namedFinally, they discovered Edward Henrywhere the thieves lived. discoveredThe gang was one step a systemahead, though. When to classify Unwashed dishesdetectives raided their ﬁngerprints.apartment, it was empty. The thieves were gone. In 1901, he became a police The police searched the apartment, but they commissioner andcould ﬁnd no trace evidence. The entire place had used his system tobeen wiped clean, but not quite. The thieves had identify criminals.forgotten to run the dishwasher. A forensic What evidence could the police ﬁnd scientist uses black powder in the dishwasher? and a brush to ﬁnd ﬁngerprints on a mug. 11 12
Criminals know this, and many are carefulClassifying Fingerprints to leave no ﬁngerprints behind. When crime Edward Henry based his system on features that everyﬁngerprint shares. Every print has ridges (the raised lines) and scene investigators (CSIs) searched the thieves’furrows (the low spots between ridges). And every print has apartment, at ﬁrst they found no ﬁngerprints.arches, loops, and whorls. Arches are either tented (pointed It looked as if the thieves had carefully wipedat the top) or plain (rounded). Loops are either radial (running the whole place clean, ﬂoor to ceiling. However,toward the thumb) or ulnar (running toward the little ﬁnger). the CSIs got ﬁngerprints from the dishes in theWhorls are circular. Henry added smaller features to his system, known as forks, dishwasher and matched them to prints in thedots, islands, hooks, and bridges. All together, the type, number, database. The robbers were caught because ofand position of these features make each ﬁngerprint unique. their dirty dishes.Type 1 Type 2arch loop dots What type ofType 3 fork ﬁngerprintwhorl is this? island Henry’s basic system is still used today. Police have about 50 million ﬁngerprints in computer databases. Prints found at crime scenes can be compared quickly with all the prints in the databases. When a match turns up, police have a piece of evidence that places a person at the scene A technician uses a computer database to match ﬁngerprints of of a crime. suspects to crimes. 13 14
Case File #3 Place: Oklahoma, U.S.A. Date: April 19, 1995 Crime: a federal building is blown up Evidence: a truck axle This part of a truck’s vehicle identiﬁcation number gaveThe Crime investigators evidence used to solve the bombing case. The crime scene investigatorssometimes have only a small How the Case Was Solvedapartment to search. But Murrah Federal Building, Oklahoma City After searching for days, investigators ﬁnallysometimes the crime scene is found a small piece of a truck’s axle. The rear axlehuge. In this case, the CSIs had several city blocks belonged to the truck that carried the bomb. Thecovered in thousands of tons of rubble to search rear axle of every truck has a vehicle identiﬁcationfor clues that would lead them to a suspect. number (VIN) in the metal. This piece of axle had At 9:08 on the morning of April 19, 1995, an only part of the VIN, but it was enough to leadexplosion rocked downtown Oklahoma City, investigators to a truck rental ofﬁce in JunctionOklahoma. A truck carrying a 5,000-pound bomb City, Kansas.exploded, blowing away the front of the nine-story The clerk remembered renting the truck to aMurrah Federal Building. The blast killed 168 man named Robert Kling. The name was false, butpeople and injured more than 500. The bomber set the clerk remembered what the man looked like.off the blast by remote control and drove away. A forensic artist made a sketch from the clerk’s description, and the owner of a nearby How could a truck axle lead investigators motel recognized the face. The man had rented a to the suspect? room from him and had used the name Timothy McVeigh. 15 16
Investigators ran the name through a national Locard’s Exchange Principlecrime computer database and came up with Edward Heinrich did his work in a crime lab, a rooma match. A man by that name was being held ﬁlled with scientiﬁc equipment used to help discover andon a trafﬁc and weapons charge in the Perry, study forensic evidence.Oklahoma jail—and was about to be released. The world’s ﬁrst crime lab was set up in 1910 in Lyons, France, by police detective Edmond Locard. Investigators got there just in time. The Locard stated a guiding principle that today’s forensicOklahoma City bomber was caught, thanks in scientists still follow. He called it the Exchange Principle: “Objects or surfaces that come into contact alwayslarge part to the work of forensic investigators. exchange trace evidence.”Timothy McVeigh was later tried, convicted, and In other words, everyone who enters a crimeput to death for the bombing. scene takes away something from the scene and leaves something of themselves behind. Locard, you’ll remember, was the detective who solved the ﬂour mill murder case.The forensic artist’s sketch, inset, led investigators to Timothy A forensic scientist works in a lab more modern thanMcVeigh, above center. that of Edward Heinrich. 17 18
Case File #4 Place: England, U.K. Date: 1993 Crime: armed robbery of $100,000 Evidence: a nylon stocking used as a maskThe Crime A view of skin under a microscope isn’t the same as a microscopic The scene of this crime is picture that makes a DNA proﬁle.the ofﬁce of a manufacturing nylon mask no maskcompany in England in 1993. How the Case Was SolvedThe $100,000 cash used to pay workers is in theofﬁce when an armed robber breaks in and carries When the robber pulled off his mask back inoff the money. 1993, twenty-ﬁve of his skin cells came off with it. In 2004, eleven years later, scientists were able Crime scene investigators found no to make a DNA proﬁle from the stored skin cells,ﬁngerprints in the ofﬁce. The only piece of which led police to a suspect named Andrewevidence left behind was the robber’s mask, Pearson.a woman’s black nylon stocking. Unlike theoveralls in Case No. 1, the stocking had no At Pearson’s trial in 2004, a forensics expertpockets or seams where trace evidence could be showed that his DNA proﬁle was an exact matchdiscovered. for the proﬁle from the skin cells on the robber’s mask. What were the chances that these skin cells could have come from another person and not What tiny bits of evidence might be left Pearson? A billion to one, the expert said. on the stocking? Pearson was convicted of the 1993 robbery and sent to prison. 19 20
Conclusion DNA Proﬁling Modern scientists and engineers keep inventing new Each of the four cases in this book deals with and better ways to gather forensic evidence. The most a different kind of forensic evidence. There are important new way is known as DNA proﬁling. DNA is the part of each of your body’s cells that other kinds of forensic carries instructions that tell your body how to live and evidence, too—footprints, grow. About 98 percent of these instructions are the shoe prints, palm prints, same in all people. The 2 percent that are different lip prints, bite marks, paint make your DNA unique, just like your ﬁngerprints. chips, tire tread marks, the Scientists can make microscopic, X-ray pictures of unique DNA, known as DNA proﬁles. Police have markings on a bullet, and tire tread marks more. Any of these can link developed computer databases of DNA proﬁles, just like ﬁngerprint databases. suspects to the scene of the DNA can be collected from almost any cell in your crime, or can show who body, including cells in your hair, saliva, blood, sweat, is innocent. and tears. Police hoped to gather DNA evidence from the robber’s stocking. They failed in 1993, but in 2004 bullet Together, the law things were different. DNA technology had advanced so enforcement ofﬁcers that even a single skin cell could produce a DNA proﬁle. and scientists who gather and study forensic evidence use virtually all of the sciences, from anthropology to shoe print zoology, in their work. Whatever science they specialize in, they all have one thing in common. Like the ﬁctional Sherlock Holmes, they use their knowledge to see what goesA computer is used to match DNA proﬁles. unnoticed by the rest of us. 21 22
Glossary ﬁngerprints the unique patterns of ridges and furrows on the tips of ﬁngers and thumbs (p. 12)convict to prove guilty of a crime (p. 4) forensic the areas of science that apply to a courtcrime lab place where scientiﬁc materials, such as science of law, often proving guilt or innocence microscopes and chemicals, are used to (p. 5) analyze forensic evidence (p. 18) informers people who secretly give informationcrime scene place where a crime has been committed about a crime, often for a reward (p. 5) and where investigators look for evidence to solve it (p. 18) microscopic so small that it can only be seen with a microscope (p. 21)crime scene law enforcement ofﬁcer who investigatesinvestigator a crime scene to search for forensic suspect a person who is believed guilty of a crime(CSI) evidence (p. 14) (p. 4)deduction a speciﬁc conclusion made from general trace dust, hairs, threads, and other bits of evidence (p. 6) evidence material used as forensic evidence (p. 4)DNA deoxyribonucleic acid; a single molecule vehicle unique multi-digit number imprinted on in a cell containing the instructions for identiﬁcation a car or truck (p. 16) growing and operating a living organism number (VIN) (p. 21) victim someone harmed by an act or condition,DNA proﬁle X-ray photograph of a section of DNA such as a crime or war (p. 4) that positively identiﬁes the person it came from (p. 20) IndexExchange Edmond Locard’s idea that objects or crime lab, 18 Henry, Edward, 12, 13Principle surfaces that come into contact always DNA, 21 Holmes, Sherlock, 5, 6, 9, 22 exchange bits of trace evidence (p. 18) DNA proﬁling, 20, 21 Locard, Edmond, 4, 18eyewitnesses people who have seen something happen Exchange Principle, 18 McVeigh, Timothy, 16, 17 such as a crime or accident (p. 5) ﬁngerprints, 12–14, 19, 21 Oklahoma City bombing, 15–17 Heinrich, Edward, 8–10, 18 trace evidence, 4, 11, 18, 19 23 24
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