Top-of-Letter Handwriting Analysis

Each person’s style of handwriting is unique and can be identified, often even if a person is trying to disguise his or her handwriting. Try the following activity to see one way handwriting is analyzed.

Materials

- pen or sharp pencil
- sheet or white paper
- sheet of tracing paper
- ruler

Procedure
1. Write your name two times on the sheet of white paper.
2. Place the tracing paper over your signature.
3. Make a small mark on the tracing paper at all of the high points of each letter in each signature.
4. Use the ruler to join each mark to the one next to it, creating a zigzag line across the top of each signature.
5. Make a top-of-letter analysis by comparing the two zigzag lines. Are they similar?

More Fun Stuff to Do

Write your name on another sheet of paper. Have a helper forge (copy with the intent to deceive) your signature 1 to 2 inches (2.5 to 5 cm) below your real signature. Make a top-of-the-letter analysis of the two signatures. How do they compare? Could this method of handwriting analysis prove that your helper’s signature was forged?

Explanation

An individual’s handwriting depends on several things, such as the brain, the eye, and the hand of the individual. It is affected by a person’s physical and emotional well-being, the position in which he or she is writing, and circumstances that might influence speed. Normally, a person’s handwriting will be slightly different from signature to signature. So, is a series of signatures on checks are exactly the same, it may indicate that someone forged the signatures by copying or tracing them. If the signatures are very different, however, this can also indicate that the signatures are fakes.

A signature in often all that is needed to withdraw money from a bank account, to write a check, or to make a purchase with a credit card. These are most common situations in which forgery, the act of falsifying documents, occurs. Every year, millions of dollars are lost to forgeries. Forgeries are found by comparing the signature in question with a known example of a person’s handwriting. For example, banks and credit card companies keep a file of copies of their customer’s signatures, and if they think that a check or credit slip might be a forgery, they will compare the signature in question with the signature in their files. If the signatures are different, they will call the police for a complete investigation. Forensic scientists will then do an even more thorough analysis of the signatures.

Indented Paper

If another piece of paper is directly under the piece that is written on, the paper underneath will pick up an impression of the writing. This can be valuable evidence for a detective who is looking for clues in a missing-person case or trying to match the origin of a ransom note in a kidnapping case. Try the following activity to see how this technique is done.

Materials

- several sheets of white paper
- ballpoint pen
- lamp or other light source
- pencil

Procedure

1. Stack the paper. Use the ballpoint pen to write an address or a phone number on the top sheet of paper.
2. Remove the top sheet, then hold the second sheet of paper up to the lamp. Can you see anything?
3. Lay the second sheet flat. Use the edge of the pencil lead to lightly shade over the place where the writing was made. Can you read the address or phone number on the second sheet?

More Fun Stuff to Do

Repeat the experiment, using different types and amounts of paper, and exerting either more or less pressure while writing. Do these changes affect your ability to read the writing on the second sheet of paper?

Explanation

How well the impression can be read will depend on a number of factors, such as the thickness of the paper, whether the sheets were on a hard or a soft surface, and the amount of pressure exerted by the writer.

If an indented sheet is found as evidence at a crime scene, this technique can be used to match it to a threating letter or a ransom note. If a diary or a business ledger with pages torn out is found, this technique can also be used to determine what was written on the missing pages.

Decomposition

Decomposition is the natural pprocess of decay. Often the decompositon of materials surrounding a body can give a forensic scientist valuable information. Not all materials decompose at the same rate. Organic material, which is material from plants or animals, decomposes differently from inorganic, or man-made, material. Forensic scientists can study the state of decomposition of these materials to approximate time of death. Try this activity to learn materials can decompose at different rates and how that information can help solve crimes.

Materials

- clear plastic 2-qurt (2-liter) soda bottle
- scissors
- cheesecloth
- rubber band
- tape
- 2 cup (500 ml) sand
- 2 quarts (2 liters) garden soil (from an outdoor location)
- organic material, such as leaves, twigs, grass, shredded newspaper, and needles
- inorganic materials, such as Styrofoam, plastic, and scraps of fabric or leather
- pen or pencil
- notebook
- rubber gloves
- several sheets of newspaper
- stick
- worms (optional)
- tap water
- adult helper

Procedure

NOTE: This activity requires adult help.

1. Remove the label as best you can from the plastic soda bottle.
2. Have your adult helper cut the bottle into two sections, making the cut approximately one-third of the way from the bottom.
3. Cover the mouth of the bottle with cheesecloth and secure it with the rubber band.
4. Turn the drop section of thebottle upside down and place it in the bottom section as shown. Tape the two sections together.
5. Put the sand in the upside-down container. Place a 1-cup (250 ml) layer of the garden soil on top of the sand.
6. Look at the organic and inorganic materials. Which items do you think will decompose quickly? Why? Whicj items do you think will take longer to decompose? Why? Record your predictions in your notebook.
7. Add a small amount of each organic and inorganic materialto the container, then add another layer of soil. Continue to layer organic and inorganic materials and soil until they reach the top of the container. Add more materials on top of the last layer of soil.
8. Add worms to the container, if you like.
9. Pour water into the container until it starts to drip through the cheesecloth.
10. Set the container where it will not be disturbed for a month. Water the container twice a week.
11. Observe the container every other day. Record your observations.
12. After a month, put on the rubber gloves and pour the contents of the container onto the newspaper. Use the stuck to move the soil arround. Observe the condition of the organic and inorganic materials. Were your prediction correct?

CAUTION: Always wear rubber gloves when examining the experiment materials. Return worms to the earth and throw out the rest of the project when you are finished. Be sure to wash your hands thoroughly when you are done.

Explanation

Decomposition is nature’s way to recycle organic, or living, material. Organic material is broken down into nutrients that can be reused by plants as they grow. Some inorganic, or nonliving, material is broken down as well, but usually at a slower rate. Bacteria, fungi, worms, and microorganisms all help to break down these materials.

Worm in particular help to speed up the process of decomposition. They make extensive networks of tunnels that help air and water reach the roots of plants. The tunnels also provide air and water for other soil-dwelling insects and small organisms that help with the process of decomposition. Worms also turn the soil by moving deep soil up to the surface and by dragging plant materials underground. One cup (250 ml) of soil may contain more than 5 billion living creatures!

Forensic scientists use their knowledge of the decomposition rates of various substances to help solve crimes in several ways. For example, the state of decomposition of a letter found behind a house could link a suspect to the time of robbery, while a rotting apple core could be an important clue for police looking for a lost camper.

Heat Loss

There are many timesthat the temperature of an object plays an important role in solving a crime. Heat from the engine of an automobile may indicate that it has just been driven. A warm cup of coffee on a kitchen table may mean that a suspect has just left. The temperature of a body can indicate to detectives when a death has occurred. Try the following activity to see how temperature can be used by forensic scientists.

Materials

- 2 cup (500 ml) of hot coffee
- coffee cup
- thermometer (measures up to 212oF [100oC])
- stopwatch or watch with second hand
- pen or pencil
- notebook
- adult helper

Procedure

NOTE: This activity requires adult help. Have your adult helper keep the hot coffee at the same temperature throughout the experiment by placing it on a stove or hot plate.

1. Have your adult helper pour 1 cup (250 ml) of hot coffee into the coffee cup.
2. Put the thermometer in the coffee, start your stopwatch, and record the temperature of the coffee in your notebook.
3. Continue to record the temperature of the coffee at 1-minute intervals until the temperature no longer changes. Empty the cup of coffee.
4. Leave the room. Have the adult helper pour another cup of hot coffee into the coffee cup and note the time that he or she pours the coffee.
5. Have the adult helper wait several minutes before inviting you back into the room.
6. Take the temperature of the coffee. Compare the temperature to your records. How many minutes has it been since your helper poured the coffee into the cup?

Explanation

When the object is removed from a source of heat, its temperature begins to drop. It cools rather rapidly until it reaches the temperature of the surrounding air, at which point its temperature stabilizes. The heat loss of the same size of object at the same initial temperature occurs at the same rate each time. This allows one to determine, with some degree of accuracy, the time that the object was removed from the heat source. In this activity, as long as the same amount of coffee at the same initial temperature was poured the second time, and as long as the room temperature did not change, you should have been able to estimate the time the coffee was poured.

At death, a body stops generating heat and its temperature drops gradually. At first the cooling is relatively rapid –approximately 1.5oF (0.8oC) per hour—but this rate slows after a few hours. In addition to size, initial temperature, and the temperature of the surroundings, body type will also affect the cooling rate. A thin body will cool more rapidly than a heavier one. By taking a body’s temp[erature, a forensic scientist can estimate the time of death.

Microorganism

Very small plants and animals called microorganisms are found on land and in the water. Like microbes, seeds, and spores, microorganisms can be important in an investigation. Try the following activity to investigate microorganisms that are found in water.

Materials

- large glass jar with lid
- water from a pond or lake
- magnifying lens
- microscope (optional)

Procedure

NOTE: This is an outdoor activity

1. Use the jar to collect some water from a pond or lake, then put the lid on the jar.
2. At home, use the magnifying lens or microscope to examine the water for microorganisms. How many different microorganisms can you find?
NOTE: Many of the microorganisms are clear or light-colored and are very small, so you will have to look carefully. They may appear to be small that move!

Explanation

Small plants and animals live in the water are the foundation of all life. These microorganisms are eaten by larger organisms, which in turn are eaten by still larger organisms. This food chain allows many different organisms to live on earth.

Microorganisms found in the water can give valuable information to a detective. Microorganisms called diatoms (microscopic algae that contain a sandlike substance called silica in their cell walls) are very important. The presence or absence of diatoms in a dead body found in water can tell forensic scientists whether the victim drowned or died before entering the water. When death is caused by drowning in natural water, such as lakes and rivers, the water in the body, aspecially that in the lungs but even water in the bloodstream, will contain diatoms. If the victim was already dead when the body entered the water, no diatoms will be found.

In investigations in which a body is found in a different location from where it drowned, forensic scientists study diatoms to determine with considerable accuracy the area of origin. This is because there are over 15,000 species of diatoms, and any combination of them found in a sample is like to be unique.

Dust and Dirt

Dust, dirt, and soil can be important evidence in an investigation. Try the following activity to see how dirt can be used to solve a crime.

Materials

- dirt from three location
- plastic bags
- marking pen
- 3 sheet of white paper
- magnifying lens

Procedure

NOTE: This is an outdoor activity.

1. Collect dirt from three locations. Place it in the plastic bags and mark the location on each bag.
2. At home, place a dirt sample from each bag on separate sheets of white paper. Examine the samples with the magnifying lens.
3. How are the dirt samples different? Is the soil light or dark? What does the soil look like? What size are the gains in the soil? Do you see any stones? Is there any decaying plant material in the soil? What characteristics could you use identify the dirt from a particular place?

Explanation

Soil is one-half air and water, both of which are necessary for plants and animals to live. The rest of soil consists of recycling organisms-such as fungi, molds, bacteria, and earthworms- pieces of rock, and humus (decaying plant and animal matter). The size of the soil particles determines whether soil is sand, silt, or clay. Sands has the largest soil particles and clay has the smallest.

All this information can be used to study soil samples found at a crime scene. Dust and dirt are common as trace evidence because they are easily carried from the scene of a crime in the soles of shoes, on clothing, or on the tires of a vehicle. Forensic scientists compare the dust and dirt found at a crime scene with selected samples to determine where they came from.

Detective Science in Action

In 1977, Janie Sheperd had been missing for four days. Her car, discovered on a London street, had been driven roughly 75 miles (120 km) from her home. By analyzing thick deposits of mud found undermeath the vehicle, investigators determined that the car had been driven in one of four surrounding counties, which greatly narrowed the search area.

Seed and Spores

Small seeds found on the suspect’s clothes or in a vehicle driven by the suspect can be important clues to where that person has been. Try following activity to see how this type of information is used to solve crimes.

Materials

- a pair of old wool socks
- field with weeds or bushes
- white paper
- magnifying lens


Procedure

NOTE: This is an outdoor activity

1. Put the wool socks on over your shoes and walk around the field.
2. Remove the socks and observe them. You should find many seeds stuck to the socks.
3. At home, pick off the seeds from the socks and put them on the white paper. Observe the seeds with the magnifying lens. How many different types of seeds did you collect?
4. Group the seeds so that similar ones are together. Can you guess which plants the seeds came from?

More Fun Stuff to Do

Plant the seeds you collected to see what kind of plants will sprout. To make sure the seeds will sprout, before planting them place them in a plastic bag in the refrigerator for a week. (Most seeds in the wild are used to going through a cold winter before sprouting). You can either remove the seeds from the socks and plat them in a pot filled with soil or fill the socks with soil, water them, and place the soil-filled socks on an old plate. Create your own Chia socks!

Repeat the original activity in a different field with different socks. Compare the seeds found in each field. How are they different? Can you tell by looking at the seeds found on the socks which field they came from?

Repeat the original activity in a different season of the year. Compare the seeds found in each season. How are they different?

Explanation

The kinds of plants that grow in a particular area determined by several factors, such as soil type, amount of water, and temperature. Most plants go through a growth cycle each year. In the spring, the plants sprout, begin growing, and then bloom, or flower. They continue to grow rapidly in the summer. In the autumn, the plants get ready for their quiet period.

Grasses and many weeds release seeds into the air or onto the ground in the preparation for the next spring. During the winter, the plants are dormant, meaning that they are alive but asleep. In the spring, seeds will sprout and the cycle begins again.

Seeds come from complex plants like grasses, bushes, and trees. Simple plants like bacteria, algae, mosses, and ferns produces spores, which are small cells that can develop into a new individual.

Using seeds and spores can be an effective way to help identify where a suspect has been walking and to link him or her to the scene of a crime. For example, if seeds found stuck to a suspect’s socks match seeds from grasses near a warehouse robbery, the evidence shows that suspect had the opportunity to commit the crime.

Microbes

Our body carry organisms that are too small to see. These creatures, called microbes, can be used to identify whether a suspect wore certain clothing or whether he or she was at the scene of a crime.

Materials

- ½ cup (125 ml) tap water
- saucepan
- 4 packages of unflavored gelatin
- timer
- clean 1-quart (1-liter) jar with lid
- trash can
- tennis shoes
- cotton swab
- rubber gloves
- dishwashing liquid
- adult helper

Procedure

NOTE: This is an outdoor activity and requires adult help.

1. Have your adult helper prepare the gelatin by boiling water in the saucepan and dissolving the gelatin packages in the boiling water.
2. Allow the gelatin to cool until it is enough to handle but not solid (about 5 minutes).
3. When the gelatin has cooled, pour it into the jar.
4. Hold the jar over the trash can. Tip the jar on its side and let the excess gelatin pour out.
5. Set the jar on its side and leave it undisturbed for 4 hours.
6. Put the tennis shoes on without socks and go play outside for at least 30 minutes.
7. Remove the shoes. Take the cotton swab and rub it between all your toes.
8. Reach into the jar and carefully brush the gelatin with the cotton swab so that you makle a wavy line in the gelatin as shown.
9. Wash your hands and feet.
10. Place the lid on the jar and put the jar in a warm, dark location. Leave it there for 4 days.
11. After 4 days, observe the gelatin in the jar. What do you see?
CAUTION: Do not touch the gelatin! Don’t keep the jar longer than four days.
12. When you are done with the experiment, put on the rubber gloves, fill the jar with hot water, let it soak for 5 minutes, and then wash the jar. The gelatin will dissolve and can be washed down the sink.
CAUTION: Be sure to wash your hands thoroughly when you are finished.

Explanation

The side of your shoes is warm, dark, and damp from sweat. This is a perfect environment for microbes to grow, as they like warm, dark, damp places. Your jar had a similar environment. The gelatin provided food for the microbes that were on your feet. Having food and a nice place to live allowed the microbes to eat and reproduce.

After four days, you should have been able to see grooves in the gelatin where the microbes had eaten it. Sometimes you might have seen different colors, depending on the type of microbe that was living on your feet and on the gelatin. If you could look at microbes under a microscope, you would see that they have unique characteristics, such as size, shape, color, and reaction to certain chemicals.

Microbes can be found not only on the inside of shoes, but on the soles of shoes and your skin as well. Forensic scientists compare microbes found at a crime scene to known microbes and to those found on a suspect. If the microbes match, they can be used to place the suspect at the crime scene.

DNA Testing

If cells, such as blood cells, are found at the scene of a crime, forensic scientists can perform a test called DNA profiling to attempt to link the cells to a certain suspect. DNA profiling is one of the most important discoveries in recent scientific history. DNA profiles look similar to the bar codes found on the products we buy. Try the following activity to simulate how DNA profiles are compared.

Materials

Bar code shown

Procedure
1. Observe the bar codes shown.
2. Match the mystery bar code to bar code A through D.


Explanation

The mystery bar code is identical to bar code C. Just as bar code contain information about the identification of a product, DNA profiles contain coded information about the make up of a human being. DNA (deoxyribonucleid acid) is a basically the blueprint or recipe for the human body. DNA is located in the nucleus (center) of every human cell. Every cell in the human body has 46 chromosomes, which contain coded information arranged into groups called genes. This coded information is a person’s DNA. Each person’s is unique, so only very small samples are required for analysis.

DNA analysis, which can be doen by the crime lab or an independent laboratory, is a complicated procedure. It involves the following steps:

1. DNA is removed from the cell nucleus.
2. The DNA strands are separated from the rest of the cell parts and chopped into smaller pieces.
3. The human DNA pieces are combined with radioactive DNA. This allows the forensic scientist to track the pieces of human DNA later.
4. The DNA pieces are separated from one another into bands according to size, using gel electrophoresis, a process similar to chromatography. (See project Ink Identification, for more information about chromatography).
5. X-rays are taken of the separated DNA pieces (the radioactive DNA will be easily seen on the X-ray) to record the individual’s DNA profile.

Just as you compared bar codes, forensic scientists can compare a DNA profile obtained from cells found at a crime scene to the DNA profile of a known suspect, to determine whether the suspect was at the scene of the crime. Examples of DNA profiles are shown.

We hear in the news about forensic experts performing DNA tests in spectacular court cases. However, the greatest number of DNA tests are routinely conducted to establish the identity of a father or a child, or to prove or disprove family relationships in immigration applications.

Feet and Inches

Even the bones of the feet can tell you a lot about the person they came from. Try the following investigation to see what feet reveal about a person’s height.

Materials

- tape measure
- pen or pencil
- paper
- calculator
- several helpers

Procedure

NOTE: This activity works if the helpers are older people who have stopped growing, rather than young children.

1. Have each helper remove his or her shoes. Use the tape measure to measure the height of each helper in inches (cm). Write each person’s name and height on the paper.
2. Have each helper stand with his or her left heel against the wall and perpendicular to the wall.
3. Carefully measure the length in inches (cm) of each person’s left foot, from the wall to the big toe. Write that information next to each person’s name and height.
4. Look at the numbers. Do you notice a pattern?
5. Use the calculator to divide the length of each person’s left foot by his or her height. Multiply the result by 100. What result do you get?

More Fun Stuff to Do

Have a helper stretch his or her arms out sideways as far as they can go. Measure the distance from the tip of the middle finger on one hand to the tip of the middle finger on the other. Compare that measurement to your helper’s height. What do you notice?

Explanation

The results of your calculation in step 5 should all have been approximately 15. For example, if a person is 63 inches (160 cm) tall and his or her left foot is 9 ½ inches (24 cm) long, the result would be 9 ½ inches (24 cm) divided by 63 inches (160 cm) times 100 equals 15. This means that the length of a person’s foot is about 15 percent of his or her height.

If a forensic scientist had to identify a person using only the bones of the foot, he or she could approximate the height of that individual using this technique. This is because the bones in the body grow at certain rates and are in proportion to one another.

Thus, in the More Stuff to Do section, the distance between the tips of the middle fingers when the arms are out stretched is the same as a person’s height. As a person’s grows taller, the feet grow bigger and the arms grow longer at the same time. By the time he or she is full grown, foot length and arm span will give approximate values for height.
These values are not always true as people grow. The ratio of one body part to another will change greatly throughout childhood. For example, the circumference of the head of a newborn, is about 25 percent of the baby’s height, while that of an adult is only about half that value.

Bone Identification

Bones can tell a great deal about the life of people who died. They can give hints about their ancestry, sex, age, and stature (height), and often they help identify someone. Bones in a criminal investigation can give clues about the time and manner of death. Try the following activities to learn more about bones and what they can tell you.

Materials

- 2 stockpots, one with lid
- tap water
- whole chicken
- timer
- tongs
- platter
- ½ cup (125 ml) baking soda
- scrub brush
- adult helper

Procedure
NOTE: This activity requires adult helper.

1. Fill one stockpot halfway with water. Put the chicken in the pot and cover it with the lid.
2. Have your adult helper set the pot on the stove burner, set the heat to medium, and boil the chicken for 2 hours.
3. Have your adult helper use the tongs to transfer the chicken from the pot to the platter. Let the chicken cool. When the chicken is cool, remove as much meat from the bones as possible.
NOTE: Have your adult helper save the good parts of the meat for a meal.
4. Fill the second pot halfway with water. Add the bones and the baking soda.
5. Ask your adult helper to boil the bones for 1 hour. This should remove all remaining meat from the bones.
6. Allow the water to cool, then transfer the bones to the platter. Use the scrub brush to clean the bones.
7. Examine the bones. How are they like? How are they different? If you were given only ane bone from the chicken, would you know where in the chicken it came from?
8. Use the diagram to help you reconstruct the chicken skeleton.

Explanation

Forensic anthropologists study the bones of the dead. They use the same techniques and discoveries to help solve twentieth century crimes as other anthropologists use to unveil the secrets of ancient civilization. Indeed, many of the nation’s forensic anthropologists spend much of their time digging into remains of ancient times.

One the first things that forensic anthropologist must determine is whether a bone is human or animal. This is often more difficult than it sounds. Some other mammals have bone very similar to human bones. For example, the bones in a bear paw look almost exactly like the bones in the human hand. Investigators also need to know whether bones are recent or ancient. This will help them determine whether the bone comes from a place of historical significance or the scene of a crime.

The skull can be used to help re-create what a person looked like. Forensic sculptors use computers to help put flesh and skin on a skeleton and thus match a skull to a photograph of a missing person. These techniques have been used to give other anthropologists an idea of what dinosaurs looked like.

The skeleton can give many important details about a person, including his or her occupation. For example, the bones of waiters and tennis players show signs of arm strength, with greater development on their strong side. Male pelvic bones (the bones that from the hips) are different from those of the female. Men’s pelvic bones are narrow and steep while women’s are shallower and broader. Forensic anthropologists often use the features of the eye sockets and nose cavity to categorize people in one or more continental or ancestral groups.

One of the best collaborative efforts in the science world is that between the Smithsonian Institution’s Department of Anthropology and the FBI in Washington D.C. Here, pure science and hard-nose police work team up to help solve some of the most tantalizing of humanity’s past and present.

Teeth Impressions

Teeth and teeth impressions can be used in an investigation to identify an unknown person and to learn information about him or her. Try the following activity to learn more about what teeth can tell you.

Materials

- scissors
- Styrofoam plate
- Marking pen

Procedure

1. Cut the Styrofoam plate into six equal wedges.
2. Stack two of wedges together, and cut 1 inch (2.5 cm) from the pointed end of both. Throw away the pieces that you cut off.
3. Slip the cut ends of the two wedges into your mouth. Push them in as far as possible while still being comfortable.
4. Bite down on the wedges firmly, then remove them.
5. Label the top wedge Impression of the Top Teeth and the bottom wedge Impression of the Bottom Teeth.
6. Examine the teeth impressions. How many teeth made marks in the top impressions? How many made marks in the bottom impressions? What features of the impressions are useful in telling the top teeth from the bottom teeth? How are the teeth different?

More Fun Stuff to Do

Collect teeth impressions from several helpers. Be sure to label each impression with the person’s name whether it is the top or bottom teeth. Leave the room, then have one helper take a bite from a piece of cheese or hard chocolate. Can you identify who took the bite by comparing the impression in the cheese or chocolate to the set of impressions?

Explanation

Humans are provided with two sets of teeth, which appear at different times in life. The first set, called deciduous teeth, appear when we are children. The second and final set, the permanent teeth, appear later and replace the deciduous teeth.

This process of replacement begins at about age six, when we lose our front incisor teeth, and continues to about age eighteen, when we get our third set molars, commonly called our wisdom teeth. We have twenty deciduous teeth: four incisors and two canines (which cut or tear food) and four molars (which chew and grind food) in each jaw. We have thirty-two permanent teeth: four incisors, two canines, four premolars, and six in each jaw.
The arrangement of each person’s teeth is unique and can be easily used to help identify a person. The number and type of teeth are valuable in determining the age of the individual. Forensic dentists can compare teeth impressions to dental records. Eighty percent of time, teeth impressions are used to identify unknown victims.

Detective Science in Action

Teeth impressions have used to identify many criminals. One hungry burglar was caught because of a half-eaten piece of cheese he left at the scene of the crime. The burglar became hungry during a break-in and took a piece of cheese out of the refrigerator. He had just taken one bite from the cheese when he heard a noise. Startled, be dropped the cheese and ran out of the house. When police arrived, they found the cheese. They matched the teeth impressions of the suspect to the bite marks in the cheese.