Forensic Science
Shodor > SUCCEED > Curriculum > Workshops > Forensic Science

Handwriting Analysis

Objective: Students will learn about the forensics of handwriting analysis while using a graphics program to compare two handwriting samples.

Materials: Each student will need

  • A sheet of tracing paper
  • A computer with GIMP and handwriting samples saved on the Desktop.

Explorations questions for students:

  1. Questions that will drive students towards what they are supposed to learn from this section.

Elements of Handwriting

  1. There are four general categories by which handwriting can be analyzed and compared:
    • Form: The shapes, curves, and angles of the letters themselves.
    • Line Quality: How hard and steadily the pen is pressed on the paper.
    • Arrangement: The spacing and formatting of the words within the paragraph.
    • Content: The spelling, grammar, and sentence formation. People usually repeat spelling and grammatical mistakes.
  2. According to research done with a very large sample of writers, none were identical in all of these characteristics.
  3. So our handwriting is as unique as our fingerprint. So why is handwriting analysis questioned as a legitimate type of forensic analysis? Forgery.

How to Verify a Signature

  1. Put a sheet of tracing paper over the real and questionable signatures.
  2. Make marks at the top of each letter and draw a line connecting the dots.
  3. These lines show the slant of the signatures. Compare the slants. Can you tell if the signatures were done by the same hand?

Comparing Handwriting Samples Using GIMP

  1. Open GIMP and go to File: Open as Layers. Select the two handwriting samples you would like to compare.
  2. You should have two toolbars: "Layers" and the toolbox. If one of these is not open, go to Windows: Recently Closed Tabs and open it.
  3. Look at the "Layers" toolbar. You should have two layers, one named background. Try clicking the eye next to the background layer. If you click the space where it was it should come back. Now try clicking the eye next to the other layer. Your other text should appear. This is how you know that you have two layers.
  4. Click the layer that is not your background layer. You know that you have highlighted it because the strip will turn blue. Now anything you do will edit that layer.
  5. Look at your two writing samples. Pick a letter or a word that appears in both. We are going to cut out that letter from the non-background layer and pull it over the background layer to see if the letters match in all the characteristics we talked about earlier.
  6. Open the toolbox. If you hover over the icons in the toolbox they will tell you their names. Find the gray rectange called the "Rectangle Select Tool". Select this tool. You may have to click multiple times to select it.
  7. Select your letter/word by clicking once on the layer(make sure you have the right layer) and then clicking and dragging the rectangle across the page until it surrounds the word. Once the text is selected, go to Edit: Cut. The word should disappear from the page.
  8. Now we want to paste the text into a new layer so it is by itself. Go to Layer: New Layer. Press enter and select the new layer. Then click Edit: Paste. If you click away the visibility(the eyes) of each of the other layers, you should see the text you pasted surrounded by a checkerboard of black and gray squares.
  9. To take away the white area around the text, click on the Fuzzy Select Tool in the toolbox. It looks like a sparkler. This tool selects the areas near it that have the same color. When you click on the white space around the word, it should look like this: Then if you click Edit: Clear, all the white space should go away and you should be left with just the text.
  10. Now we are going to compare the piece of text to the original writing sample. Click the eyes so that only the new layer you just made and the original writing sample are visible. Select the new layer.
  11. You should see the original sample with your piece of text on top of it. Now you are going to use the Move tool in the toolbox. Click and drag the text above the original sample. You can put it over each individual letter and compare much more closely than if you were to just look at the handwriting samples on paper.