Bad Hair Day: Hair Analysis

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Objective

SWBAT a mystery by identifying and analyzing hair at the scene of a crime.

Big Idea

How do scientists use something as small as a few strands of hair to solve a crime? We practice analyzing hair to learn about where it came from and how it could break a case wide open!

Teacher Set-up

15 minutes

Prior to starting this lesson, you will need to collect 7 different hair samples from a variety of animals and/or people. These can be similar or different in color, texture, and length, but should be long and plentiful enough to view under a microscope. Each group will need their own set of samples, so be sure to plan accordingly and get enough of each sample to go around. Samples must include the following:

  • 2 samples from animals (labeled accurately with species)
  • 2 samples from humans (labeled accurately with species)
  • 3 samples from either human or animal (labeled as "unknown sample 1, 2, 3")

The first four samples should be prepared on slides using Permount mounting medium instead of water, which creates the best viewing conditions, at least 24 hours ahead of time. The three "unknown" sampled should be placed in plastic baggies, as students will create their own wet mount slides.

Each group also needs 1 microscope, 3-5 blank slides, 3-5 slide covers, 1 dropper or pipette, and colored pencils.

Before using student hair samples to create a simple shortcut to collecting and mounting hair samples, please read my reflection. It provides important information on why not do this.

Engage

5 minutes

I start each class period in this unit with a warm-up activity that targets forensic science concepts and other skills (observation, problem-solving, etc.) Not only does this get the students in the frame of mind necessary to address the field of forensics, but it also introduces key vocabulary they use throughout the unit in a more relevant way. In addition, this activity allows students to refine their research skills as they perform quick internet searches to find the correct answers. By using the attached weekly Answer Sheet* and passing it out as they enter the classroom every Monday morning, not only can I save paper, but I can also provide a routine that allows students to begin without prompting, waiting for paper, or asking things such as, "What do we do?" and, "Where do we write our answers?"

For this particular lesson, I have decided to utilize a Trivia Challenge*, in which students use their knowledge of forensics and their research skills to answer an assortment of trivia questions.

After providing about 2-3 minutes to look for the answers, we go over them together and discuss the information provided. I help students to define key terms and providing background knowledge necessary to help students understand the questions. However, I do not spend as extended period of time on this portion, as it is just meant to be an activator and not necessary to understanding the core of the lesson at this time.

*Challenges and answer sheet courtesy of http://sciencespot.net/Pages/classforscistarters.html

Explore

10 minutes

I have students use their laptops to play the Hair Detective Game. In this game, students investigate several hair samples to determine who stole the hair products from backstage at a boy band concert. 

While it is a little silly, it provides a good foundation to help students learn a little about the tools and variables that are used to analyze hair in a forensics investigation.

 

After playing, I have students take about 5 minutes to respond to the following questions in a quickwrite:

  • What tools can be used to analyze hair?
  • What can forensic scientists learn about hair from using these tools?
  • How does hair differ from person to person?

Explain

20 minutes

After each student has responded to the quickwrite, they pass their papers to the person on their left, and read each other's work. Each student then provides feedback (in writing) to their partner's work by using one of the following sentence stems to compose a 2-3 sentence response:

  • I agree, and...
  • I agree, but...
  • I disagree, because...
  • I wonder...

Not only does this confirm or challenge students to think deeper about content, but it provides a quick and somewhat quiet way for students to communicate. It also prepares them for the hands-on portion of the lesson by framing the process of hair analysis as providing focus to the steps involved. The students return the paper to the original owners and read the feedback that was provided.

I explain to the students that forensics scientists will often analyze hair at a crime scene to determine if it belongs to an animal or a human, which can tell them a lot about the crime that occurred, such as its location, surrounding circumstances, and details about the victim and/or suspect. Next, I pass out the Hair Analysis Information Sheet (provided by CourtTV*) and read through the information aloud as student read silently. I encourage them to highlight or underline key information as I read, but do not necessarily require it, as students will refer back and reread this document several times during the lab.

After a quick read of the document to help students understand where to identify information they will need later in the lab, I project the Microlab website and on the board and display several magnified hair samples for the students to view. These are displayed with much greater magnification than our classroom microscopes can, so this site is a great resource! As we view several hair samples on the site, I call on random students to make observations about what they see, using terminology and information from the Information Sheet. I may also ask specific questions that force students back into the text, such as:

  • What is the medulla pattern?
  • How thick is the medulla compared to the rest of the hair shaft (medullary index)?
  • Is the root visible?
  • Describe the cuticle?
  • How might you know this was an animal hair? A human hair?

*For the complete CourtTV document and curriculum, please visit Forensics in the Classroom.

Elaborate

40 minutes

I pass out the Hair Analysis Lab and explain to the students that they will get the opportunity to analyze real hair samples to determine if they belong to an animal or a human.

We read through the lab introduction and directions as a class, and I answer any questions that the students have prior to starting. Once students understand the procedures, I set students to work.

As students work through the lab, I remind them to revisit their Hair Information Sheet and the online Microlab Gallery we viewed earlier in the lesson to help them with terminology and to compare the samples they have to images of animal and human hairs. Students are directed to work through the section entitled, "Analysis", and then to stop before moving on.

When students complete the lab, I have them read the article, Your hair tells the truth about you. I provide some focus for the reading by asking them to use two different highlighters to identify specific information:

  • Use one color to highlight how hair analysis has increased what we can learn about a person
  • Use another color to highlight the problems with hair analysis

Evaluate

5 minutes

After completing the lab and the analysis questions, I ask the students to consider how accurate they believe hair analysis really is and exactly what an investigator would be able to determine from analyzing hair at a crime scene. I also ask them to consider how confident they would be if they had to try a criminal based on hair as their evidence.

After giving students to few moments to think about these questions and to discuss at their tables, I play the Flaws in FBI forensics analysis may have helped convict wrong people video:

After watching the video, I direct the students to the Conclusion portion of the lab guide and have them reflect in writing. This writing piece provided insight into the students' general understanding of the process of hair analysis, but also its shortcomings as they relates to forensic science.