Shoe Print Recognition

1. Shoe Print Recognition Crime Scene Analysis

2. What can a shoe print tell? • Size of a particular shoe – men’s size 10 • Shoe of a certain manufacturer - Nike • Shoe of a certain make – Air Cross Trainers • Size/Height/Weight of person making print

3. How accurate is it? • The print is only as accurate as the print dictates • Partial prints or prints with a lot of so called noise can be less accurate • Prints that are clear and show the shoe entirely are more accurate • Shoe prints can even identify the suspect if wear patterns and defects can be detected. • Walking with a limp • Knees turning in or out • Knee replacement/hip replacement

4. Past Analysis • Previously crime scene scientists had to make a plaster cast of a shoe print. • They would then use guides and identifying features to match descriptions of a suspects shoe. • A match would be visually identified. • This is very time consuming.

5. Analysis Now • Now a new technique is being used. • It is similar to finger print analysis. • A database of manufacturers’ shoes has been assembled by the FBI. • They have used a computer algorithm to identify various points and shapes of a shoe print and automatically identify it with the database.

6. Your Analysis • Since we don’t have the FBI’s database or algorithm, we will use old fashioned methods of identification. • We will use feature identification and classification.

7. Feature Detection • There are lots of shapes and patterns that can be found on the soles of shoes. We are only going to deal with sneakers which have a very distinct tread pattern. • Each manufacturer has their own tread pattern.

8. Aspects of Feature Detection • Locality – where is the pattern located on the sole of the shoe • Repeatability – how is it repeated on the sole • Distinctiveness- what identifiable marks such as a logo or specific shape might be on the sole

9. What is Noise? • Unidentifiable wear patterns unique to the wearer • Items stuck to the shoe as the print was found (gum, grass, etc.) • Partial or light prints • Other items that interfere with a good print such as the surface it is found on, like a carpet or a vinyl floor.

10. Time to try it…. You will receive a copy of a shoe print. The shoe print may be from someone in this class but it may not be. Your task is to match your shoe print with the prints in the database.

11. First things first… Study your shoe print and find any identifying features.

12. Identifying Features are… • Look for identifying logos (Can you see a partial Nike Swoosh – explain on your lab) • Look for repeating patterns or shapes (Can you see wavy lines across the shoe – explain on your lab) • Look for deep grooves or loss of patterns, they may indicate wear. (Can you see wear or noise – explain on your lab)

13. The Analysis • Open the database file. Search through the records and try to identify which shoe matches your shoe print. • Identify the patterns, logos, and wear features you found in your print.

14. Conclusion • Once you believe you have a match, you must support you conclusion. • Complete question 10 on the lab sheet. • Now look through the database – can you see common tread patterns among the sneakers? Complete the last question on your lab sheet.