courtesy blvesboy

Procedural crime dramas are very popular and for good reason.  They use evidence and science to analyze a mystery and uncover answers – a great metaphor for what a classroom learning experience can be.  In this apptivity, we will learn about fingerprints, create digital images of our own, and then use annotation tools to help us identify the cheesecake thief!

This apptivity will chain together using the iPad’s Camera App, photo editing features, YouTube (or built in Video), Skitch, and Keynote.


  • iPad 2 or newer (iOS 5 or better) for each group
  • Doodle Buddy
  • Skitch
  • Bump (or other photo exchange app)
  • Keynote
  • a sheet of white paper
  • a sharpened pencil
  • scotch tape

 Spoiler Alert:  You, the teacher, are going to be the thief!  Be sure to have your own thumbprint already digitized and ready to share with the students.



Your sister is on a rampage this afternoon!  Someone has eaten the piece of cheesecake she was saving for her after school snack!  It was in the refrigerator and clearly marked with her name, but now all that is left is a plate with crumbs and some smeared chocolate sauce.    Interestingly, there seems to be a chocolaty  fingerprint (perhaps a thumb?) left on the plate!  Earlier in the afternoon, you had a group of friends over to study.  Coincidentally, everyone who was there, is now in the room!  You decide to get to the bottom of who stole the cheese cake.


Present the scenario to the students.  Brainstorm ideas about how to determine who may have eaten the cheesecake.  If it isn’t offered as a possible solution, suggest that fingerprints may give us some insight.


The Fingerprinting Process:

Have each student use a pencil to create a small square of graphite on their paper.  Put it on thick so that it will easily transfer to their fingers.

Rub the pad of the thumb on the square of graphite to cover it well.

Tear off a piece of scotch tape that will cover the the pad of the thumb.  Attach it to the pad of the thumb and gently rub to get a good fingerprint transfer.

Carefully remove the tape and attach it to a clear spot on the paper.  You’ll notice that the fingerprint is clearly visible now.

Here is a tutorial with pictures of this process.

Digitize the Fingerprint

Camera App

Capture the fingerprint digitally by using the Camera App on your iPad.  This is a great opportunity to talk about how to focus on the details in the picture.  Experiment with distances from the paper to get the clearest picture.

Use the enhance, contrast, and crop editing features within the Camera App.

Repeat this process for the thumbprint found at the crime scene.


Learn about Fingerprint Analysis

There are dozens of videos online in iTunes U and YouTube which present basic information about fingerprint analysis.  I like this one:

Fingerprint Analysis Video

Have students use Doodle Buddy or another note and sketch app to capture the fingerprint analysis terms in the video.

  • Core
  • Loop
  • Arch
  • Delta
  • Bifurcation
  • Whorl
  • Ridge Ending
  • Dot


Analyze Your Own Fingerprint


Launch the Skitch App

Open a new canvas and import the photo of your fingerprint

Analyze the photo for examples of the terms from the video

Use arrows and text to annotate the photo of your fingerprint

Add your name to the top of the Photo

Repeat this process for the thumbprint found at the crime scene.


Share Your Analysis



Now we need to get all the photos of fingerprints onto all the devices.  There are several ways to share photos between students.  They may want to post them into a learning space in a learning management system, wiki or blog (Moodle, Edmodo, eChalk, KidBlog, etc.). Once posted the students could view each photo in the Safari Browser and save them by tapping and holding on it.  This may be the most efficient approach.

They could also use apps like Bump or Shake2U to exchange the files in a more social and kinesthetic way.   I like this approach because it gives them a chance to experience social learning in a very real context.


Final Analysis

This icon represents the Keynote App


Create a new Keynote presentation and add the chocolate fingerprint that was found at the scene to a slide.

Browse through the pictures you collected and look for similarities with the chocolate thumbprint.

Place any close matches to the chocolate thumbprint side by side on a slide.



Ask students to use AirPlay or connect their iPad to the classroom projector to share their findings.

Use a polling solution like to collect student opinions about who the perpetrator might be and why.