Caught Red-Handed: Fingerprint Analysis

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Objective

SWBAT list and describe the three types of fingerprint patterns and the three types of fingerprints that can be made. SWBAT explain why fingerprinting is important and useful to police in crime investigations.

Big Idea

Fingerprints are an integral piece of evidence when it comes to solving crimes. Students will learn how fingerprints are collected and analyzed within the field of forensics.

Teacher Set-up

10 minutes

Materials:

  • Crime scene tape
  • Coffee cups (ceramic works best for this activity)*
  • Balloons (uninflated; 1 per student, plus a few extras just in case!)
  • Ink Pads (black or another dark color)
  • Sharpie permanent markers (1 per student; not the same color as the ink pad or the balloons)
  • Wet Naps

I also set up student materials buckets (1 per table group) that each contain:

  • Index cards or white paper
  • Clear packing tape
  • Talcum powder (baby powder or cornstarch is fine as well)
  • Small paint or makeup brushes with very soft bristles
  • Cocoa powder
  • Magnifying glasses
  • Gloves (1 pair per student)**

 

Before students enter the classroom, I set up a fake "crime scene" throughout the classroom. This includes the following:

  • Cordon off the classroom/desks with crime scene tape
  • Scatter papers, pencils, etc. around the room
  • Coffee cups scattered around the room

 

I also write the term "biometric technology" in large letters on the board to refer to later in the lesson.

 

*Before implementing this lesson, select a few adults to touch/hold the cups, so that clear fingerprints can be made on them. Students will dust the cups for prints later in the lesson. Have these same people provide ink pad fingerprints of their thumb and index finger on white paper. I like to have other teachers participate, and have them place their fingerprints on a worksheet, test, or homework assignment form their class.


**Be aware of any latex allergies before providing gloves!

Engage

5 minutes

As students enter the room, they will undoubtedly notice the chaos ans want to know what has occurred. I tell students the following "crime" story:

  • The school was broken into overnight.
  • The perpetrator stole the coffee out of my refrigerator and helped himself to my coffee machine. (The kids know I am a HUGE coffee fan, so they will understand how serious the situation is. You can adjust this part to make sense for your class.)
  • The thief also stole all of the candy out of my secret stash!
  • S/he also left cups all over the room for me to wash!
  • We must find the perpetrator or the entire class will be required to deal with a non-caffeinated, grumpy teacher who no longer has any candy to hand out for the rest of the year!

 

I give them a few minutes to look around the room, but instruct them NOT to touch ANYTHING, as they might end up tampering with potential evidence!

Explore

10 minutes

Before starting our investigation, I ask the students to list some of the clues we might be able to find that would help us solve the crime. I accept responses until someone mentions fingerprints, which usually doesn't take too long. Once I receive this response, I ask what objects we may want to check for prints, allowing students to call out their ideas. I also ask them why fingerprints may be helpful, again allowing for call outs.

I explain to the students that fingerprints are the oldest biometric technologies, or technologies that measure and analyze human body characteristics, such as DNA, fingerprints, voice patterns, and facial patterns, and one of the most useful for forensics. As I explain, I point to this term on the board and choose a student to paraphrase and write a basic definition next to it.

I project a fingerprint timeline and further explain some of the more important points, including when people began to classify and compare fingerprints, when they were first cataloged, and when they went from paper copies to video tape storage, and eventually to a computer automated fingerprint identification system (AFIS). I also explain that today, the FBI's computer database contains over 200 million fingerprints!

I pass out the "What's Your Distinct Fingerprint" handout and have students read first paragraph  on their own. After reading, I ask the students to consider why fingerprints are so important when it comes to solving crimes. After calling on a few students to provide their insight, I explain that even though we can't always see them, fingerprints are left behind whenever we touch something. Our hands have oils and sweat. When the water from the sweat evaporates, the oil leaves a fingerprint behind.

I give each student a wet nap and an uninflated balloon, telling them not to blow it up just yet. Next, I pass a black ink pad to each table group and instruct the students to place their thumb on the pad and then on the balloon, in order to get a thumbprint on the uninflated balloon.  After allowing a few minutes for it to dry, I have them do the same thing with their index finger on the other side of the balloon. Next, I have each student blow up their balloon in order to see their fingerprint in epic proportions! After allowing a minute or two to clean their fingers with the wet naps and observe their print, I ask them to turn to their shoulder partner and identify how their prints are similar and/or different from their partner's. I give them about 2-3 minutes to discuss and then I call on one student from each group to share what they noticed.

Next, I pass out the Fingerprint Basics Card (courtesy of sciencespot.net) and have students identify the three classifications of fingerprint patterns. I have them compare their own fingerprints to the card and determine which fingerprint pattern most closely matches their own. We take a quick poll to see how many students in our class have each type of pattern and I tally it on the board.

In addition to general classification, there are small details called minutiae that are used to compare fingerprints. We read through this portion of the Fingerprint Basics card and I challenge the students to find and identify the different minutiae in their own fingerprints by using a Sharpie marker to circle them on their balloon.  

Explain

20 minutes

Now that we have learned about different fingerprint patterns and what makes each fingerprint unique, I ask the students how it is possible for investigators to analyze these prints when they are so small, and usually invisible. After all, criminals don't place their inked prints on balloons and blow them up for he world to see. Many students will have seen investigators dust for fingerprints on television, and will have a general idea how they are collected, or at least made visible. I show them the Dusting For Prints video clip (by Plymouth, MA sheriff department) to make this process more understandable.

 

Once we are finished watching the video, I pass out the Fingerprints at the Crime Scene handout and have students read the entire page. I go through each step with the students and ask clarifying questions to make sure students understand the process, such as:

  • Why is the tape necessary?
  • Why is it necessary to use talcum powder for some prints?
  • How can we be sure we don't leave our own prints?

 

Once the students have read through the process and we have clarified each step, I ask the students to identify an item they may want to dust in our classroom today in order to help us find the evil coffee/candy thief. I have one student from each table group collect a tub of supplies which includes gloves, paper, tape, cocoa powder, talcum powder, brushes, and evidence labels.I challenge each group to dust for fingerprints in order to catch the person who broke into our classroom.

Elaborate

20 minutes

After students have collected a few good prints (3-4 is enough) I have them view the Automated Fingerprint Identification System (AFIS) video.

 

Next, I explain that we will use the same technique to try to find our own "perp".  There is always one deep thinking students who will always ask how we might be able to identify a perpetrator if we don't have access to this directory. If no one speaks up, I pose that question as though I am thinking to myself aloud. 

That's when I pull out he worksheets, tests, or homework assignments from other teachers. I explain that these teachers have a vendetta against me because I would not join their break-dancing group back in the 80's, but I formed my own group and rose to fame, while they were left penniless and without rhythm. I tell the kids that I knew they would try to get revenge on me one day, so I kept these little mementos with their fingerprints just in case anything were to ever happen to me.

I pass out the worksheets and have students get to work trying to match up the fingerprints*, based on patterns and minutiae, prompting them to identify and circle or trace any irregularities with their markers. Each tub is equipped with magnifying glasses to help students see their prints clearly.

* I will usually add a few extra fingerprints from "innocent" teachers and from myself, just to throw the kids off a little. I want them to experience how difficult this really can be!

Evaluate

5 minutes

As a final assessment of their understanding, students will complete the Fingerprint Analysis. This writing activity requires students to identify a suspect and provide evidence to justify their thinking. They must use detailed information regarding the fingerprint pattern and any minutiae, which will provide insight in to their understanding of how to dust for and analyze a fingerprint in order to help solve a crime.