Crime Lab
This workshop encourages participants to think critically while exploring various techniques used in forensic science.
This workshop explores techniques used in forensic science. As a warm-up activity, participants will work in groups to brainstorm ways to estimate the height of an individual from a footprint. Afterwards, they will practice fingerprinting techniques and analyze handwriting samples. They will also experiment with chromatography by using coffee filters to separate the dyes in ink. Lastly, participants will perform a series of chemical reactions following a flowchart to identify a mystery powder.
What You Need
Refer to the Crime Lab Manual for instructions on how to facilitate this workshop as a crime scene.
Warm-up Activity: Footprints
- Measuring tape (6)
- Footprints (6)
Activity 1a+b: Fingerprinting
- White paper (1 per participant)
- Pencils (6, sharpened)
- Clear tape
- Magnifying glasses (3)
- Corn starch in a small accessible container (3)
- Paint brushes (3)
- Black construction paper, cut into small squares (1 per participant)
- Fingerprinting Task Card
- Fingerprint Patterns Card
Activity 2a: Chromatography
- Plastic tub (1)
- Masking tape (1)
- Coloured markers
- Different brands of black-ink pens
- Coffee filter paper- cut into strips (2-3 per group)
- Chromatography and Handwriting Task Card
Activity 2b: Handwriting Analysis
- Tracing paper (1 per student)
- Pencils (6, sharpened)
- Chromatography and Handwriting Task Card
- Handwriting Samples
Activity 3: Chemical Analysis
- Test tubes (6)
- Test tube rack (6)
- Small spoons/craft sticks (10)
- Water in small container (2)
- Pipette (2)
- Dropper bottle of vinegar (labelled)
- Dropper bottle of iodine solution (labelled)
- Dropper bottle of phenolphthalein solution (labelled)
- Mystery powders (Tums, chalk, Plaster of Paris, washing soda, salt, cornstarch, baking soda, sugar)
- Safety glasses (6)
- Chemical Analysis Task Card
Guide:
Safety Notes
Safety notes for Activity 3: Chemical Analysis,
- Safety goggles are required.
- Before the activity, demonstrate the proper technique for mixing the contents in a test tube (lightly tap the bottom of the tube with your finger).
- Extra caution should be taken while using glass test tubes.
- Unless instructed, do not taste or smell anything.
- Have paper towels available to clean up any spill or broken glass.
What To Do
Pre Activity Prep
- It may be helpful to cut the coffee filter paper into strips and draw a horizontal line with PENCIL before handing it out to students. You can get the students to trace it with ink.
- Have paper towels available to clean any spills.
- If setting up the activity as a crime scene:
- Prepare the evidence and suspect bags as outlined in the Crime Lab manual.
- Print Crime Lab Data Sheet (1 per participant).
- Draw the chart found on page 21 of the Crime Lab Manual on the classroom board on flip-chart paper.
Warm-up Activity: Footprints
- Using the footprint provided, determine the approximate height of the person who left the footprint. Try to think of different ways to approach the problem.
- Refer to the Crime Lab Manual for examples of different approaches to this challenge.
Activity 1a: Fingerprinting
- On a piece of paper, rub a small black patch of graphite using a pencil.
- Move your finger back and forth across the graphite, until it is blackened.
- Use a piece of tape to lift the fingerprint directly from the finger.
- Place the tape on the paper.
- Examine prints with a magnifying glass to classify the type of pattern.
Activity 1b: Lifting prints from a jar
- Place your thumb on a clear jar in order to leave a fingerprint.
- Use a small paintbrush with a very small amount of baby powder and carefully “dust” the print on the jar.
- Lift the dusted fingerprint from the jar onto a piece of black paper using a piece of clear tape.
- Examine the print with a magnifying glass.
Activity 2a: Chromatography
- Draw a horizontal line or dot on a strip of coffee filter paper using a black pen/marker. The line or dot should be about two finger widths from the bottom of the filter paper.
- Important: let the ink dry completely!
- Carefully hang the filter paper into some water, making sure that the ink line stays above the water.
- Repeat activity using different coloured pens and markers.
- Tape results into a datasheet or onto blank pieces of paper.
Activity 2b: Handwriting Analysis
- Compare handwriting samples and your own handwriting and discuss similarities and differences.
Activity 3: Chemical Analysis
Before the activity:
- Remind the group of safety protocols. All participants should be wearing safety goggles.
- Go through the task card instructions with participants and demonstrate going through the road map with one powder. Point out the difference between opaque (milky) and translucent (clear).
- Each participant should have a container with a mystery test powder (crushed Tums, chalk, plaster of paris, baking soda, sugar and salt).
- Reagents (water, iodine solution, phenolphthalein indicator and vinegar) should be in labelled dropper bottles and in an easy to reach area.
To determine their mystery powder, each participant will:
- Put a small amount of the powder into a clean test tube. Add 5mls of water and mix well.
- If the solution is opaque, add 2 drops of iodine solution. If the solution is translucent, add 2 drops of phenolphthalein indicator.
- If the opaque solution turns purple, it is cornstarch.
- If the translucent solution turns pink, it is washing soda.
- If there is no colour change, take a new clean test tube.
- Add a small amount of the same powder to 5ml of vinegar.
- If bubbles appear in the opaque powder- smell it. If it is minty, it is Tums. Otherwise the powder is chalk.
- If no bubbles appear in the opaque powder, it is Plaster of Paris.
- If bubbles appear in the translucent powder, it is baking soda.
- If no bubbles appear in the translucent powder- taste it. It is either sugar or salt.
Wrap-up
- Discuss other possible sources of evidence (i.e. DNA, witness interviews, clothing fibers, etc) and what sort of information they provide.
- If activity was set as a crime scene:
- Fill in the chart with each group’s information from their data sheet.
- Have each group make a report to you based on what they found out from each analysis OR
- Go over common results (from data sheet).
- Determine who is the criminal based on the above results. Did all groups come to the same conclusion?
- Discuss possible careers related to the topics mentioned and what they will need to do (schooling, experience, etc…) in order to get into those careers.
Post Activity
- Hand out the Forensic Science Word Search if time permits, or give it to the educator to reinforce the topics discussed in today’s workshop (optional).
- Wash and dry all dirty test tubes.
- If using suspect/evidence bags, ensure all materials make it back to the correct bag.
- Replenish any low supplies, making note of materials to purchase before the next workshop.
Discovery
Warm-up Activity: Footprints
There is a relationship between height and foot size. In general, the bigger and taller you are, the wider and longer your feet have to be in order to balance while standing. The normal height-to-foot ratio is 6.6:1, which means that for every 6.6 inches of height there is 1 inch of foot length. This is just an estimate and variations may be due to genetics or growth spurts. In a situation where someone is missing, it may be helpful for forensic scientists to determine their height by their footprint.
In this activity, participants are encouraged to think critically about how to solve a problem with limited information. Using a footprint provided, they can use the follow approaches to try to determine the approximate height of the person who left it:
- Comparing the length of their own footprint to their height. This ratio can be applied to the unknown print. For more accuracy, an average of multiple participant ratios can be used.
- Attempt to find an individual who has a similar sized footprint to the mystery footprint. The height of the individual can be used as an approximation.
Activity 1: Fingerprinting
Fingerprints are made of ridges on the upper skin on hands (and feet) on all people and some animals. These ridges make lines of different sizes and forms. Fingerprints are used for grip and in identifying individuals. There are two rules about fingerprints:
- They are permanent.
- They are unique, meaning no two fingerprints are the same.
Fingerprint patterns are classified into four main types: arch, loop, whorl and composite.
Activity 2: Chromatography
Chromatography is a technique used to separate mixtures. It involves dissolving a sample into a mobile phase (i.e. water) and forcing it through a stationary phase (i.e. filter paper). In this activity, the mixture being separated is ink. When the filter paper is dipped in water, the water molecules start to move up the filter paper and dissolve the ink. The ink consists of various coloured dyes that depending on their chemical structure may be more attracted to the paper or the water molecules. As a result, the dyes move up the filter paper at different speeds and begin to separate.
Black ink can be made from a variety of different coloured dyes and the formula can change between brands. This means chromatography can be used to distinguish the different types of ink that wouldn’t be possible to the naked eye.
Activity 3: Chemical Analysis
There are different types of chemical analysis- qualitative analysis (used to identify what is in a sample) or quantitative analysis (how much is in the sample). This activity focuses on qualitative analysis, with participants performing a series of chemical reactions to try to identify an unknown substance (flow chart).
A chemical reaction occurs when two or more substances (reactants) are mixed together, resulting in change to chemical structure of the substances (now called products). These products may have different properties (colour, smell, etc…) distinguishable from the reactants. Substances react in characteristic ways, thus the identity of an unknown substance can be determined by observing how it reacts to a specific chemical reaction(s).
Forensic science is like trying to solve a puzzle with many missing and extra pieces. Professionals use many different techniques to collect and analyze data in search of evidence that will bring them closer to the truth. It is important for conclusions to be based upon as much reliable evidence as possible. Technological advances provide new methods of analyzing data, making it possible to figure out unsolved cases years later. Examples of professionals that work together in crime lab investigation include forensic technologies and criminal investigators.
Activity Modifications
- Note: there are different ways to facilitate this workshop. Volunteers can choose to set up different stations and have participants rotate through the activities and discuss the techniques in forensic science. Another way to facilitate this workshop is to have participants analyze evidence found at a crime scene and suspect data to conclude who perpetrated the crime. Refer to the Crime Lab Manual for more information on creating the later version of the activity.
- For complexity and intrigue, evidence from two suspects can be mixed (either from one sample, i.e. the mystery powders or the entire evidence bags), which will lead groups to come to different conclusions in the wrap-up. This introduces the topic of inconclusive evidence and further demonstrates how forensic science is all about solving a puzzle with many missing pieces. It is important not to rely on just one piece of evidence, since there is so many opportunities for error.
- Alternatively, multiples of each type of evidence can be found at the scene of the crime (for example, more than 1 powder, multiple pen samples, etc…). Be sure that only the chosen culprit will have evidence found at each station. This further demonstrates the importance of collecting as much data as possible and not relying on just one piece of evidence.
Additional Resources
- You Be the Crime Scene Investigator (Lessons) - Students learn that the world of crime scene investigation (CSI) is one that is highly scientific in nature and has many career paths.
- How can I write secret messages? (Hands-on Activities) - Learn how you can write and reveal secret messages in this hands-on chemistry activity.
- How can I obtain a sample of DNA (Hands-on Activities) - Be a Biochemist! Learn how to extract DNA from an onion and find out what DNA looks like.
What's Happening?
Warm-up Activity: Footprints
There is a relationship between height and foot size. In general, the bigger and taller you are, the wider and longer your feet have to be in order to balance while standing. The normal height-to-foot ratio is 6.6:1, which means that for every 6.6 inches of height there is 1 inch of foot length. This is just an estimate and variations may be due to genetics or growth spurts. In a situation where someone is missing, it may be helpful for forensic scientists to determine their height by their footprint.
In this activity, participants are encouraged to think critically about how to solve a problem with limited information. Using a footprint provided, they can use the follow approaches to try to determine the approximate height of the person who left it:
- Comparing the length of their own footprint to their height. This ratio can be applied to the unknown print. For more accuracy, an average of multiple participant ratios can be used.
- Attempt to find an individual who has a similar sized footprint to the mystery footprint. The height of the individual can be used as an approximation.
Activity 1: Fingerprinting
Fingerprints are made of ridges on the upper skin on hands (and feet) on all people and some animals. These ridges make lines of different sizes and forms. Fingerprints are used for grip and in identifying individuals. There are two rules about fingerprints:
- They are permanent.
- They are unique, meaning no two fingerprints are the same.
Fingerprint patterns are classified into four main types: arch, loop, whorl and composite.
Activity 2: Chromatography
Chromatography is a technique used to separate mixtures. It involves dissolving a sample into a mobile phase (i.e. water) and forcing it through a stationary phase (i.e. filter paper). In this activity, the mixture being separated is ink. When the filter paper is dipped in water, the water molecules start to move up the filter paper and dissolve the ink. The ink consists of various coloured dyes that depending on their chemical structure may be more attracted to the paper or the water molecules. As a result, the dyes move up the filter paper at different speeds and begin to separate.
Black ink can be made from a variety of different coloured dyes and the formula can change between brands. This means chromatography can be used to distinguish the different types of ink that wouldn’t be possible to the naked eye.
Activity 3: Chemical Analysis
There are different types of chemical analysis- qualitative analysis (used to identify what is in a sample) or quantitative analysis (how much is in the sample). This activity focuses on qualitative analysis, with participants performing a series of chemical reactions to try to identify an unknown substance (flow chart).
A chemical reaction occurs when two or more substances (reactants) are mixed together, resulting in change to chemical structure of the substances (now called products). These products may have different properties (colour, smell, etc…) distinguishable from the reactants. Substances react in characteristic ways, thus the identity of an unknown substance can be determined by observing how it reacts to a specific chemical reaction(s).
Why Does it Matter?
Forensic science is like trying to solve a puzzle with many missing and extra pieces. Professionals use many different techniques to collect and analyze data in search of evidence that will bring them closer to the truth. It is important for conclusions to be based upon as much reliable evidence as possible. Technological advances provide new methods of analyzing data, making it possible to figure out unsolved cases years later. Examples of professionals that work together in crime lab investigation include forensic technologies and criminal investigators.
Investigate Further
Activity Modifications
- Note: there are different ways to facilitate this workshop. Volunteers can choose to set up different stations and have participants rotate through the activities and discuss the techniques in forensic science. Another way to facilitate this workshop is to have participants analyze evidence found at a crime scene and suspect data to conclude who perpetrated the crime. Refer to the Crime Lab Manual for more information on creating the later version of the activity.
- For complexity and intrigue, evidence from two suspects can be mixed (either from one sample, i.e. the mystery powders or the entire evidence bags), which will lead groups to come to different conclusions in the wrap-up. This introduces the topic of inconclusive evidence and further demonstrates how forensic science is all about solving a puzzle with many missing pieces. It is important not to rely on just one piece of evidence, since there is so many opportunities for error.
- Alternatively, multiples of each type of evidence can be found at the scene of the crime (for example, more than 1 powder, multiple pen samples, etc…). Be sure that only the chosen culprit will have evidence found at each station. This further demonstrates the importance of collecting as much data as possible and not relying on just one piece of evidence.
Additional Resources
- You Be the Crime Scene Investigator (Lessons) - Students learn that the world of crime scene investigation (CSI) is one that is highly scientific in nature and has many career paths.
- How can I write secret messages? (Hands-on Activities) - Learn how you can write and reveal secret messages in this hands-on chemistry activity.
- How can I obtain a sample of DNA (Hands-on Activities) - Be a Biochemist! Learn how to extract DNA from an onion and find out what DNA looks like.