How to Match Shoeprints to Shoe Models in Complex Background

There are two main challenges when using a crime scene shoeprint to identify the shoe that left it:

1. Whether the corresponding shoe model exists in the shoe database.

2. The complex nature of the scene often makes it difficult to recognize outsole tread patterns — especially in the case of three-dimensional shoeprints, which are even harder to analyze.

Today, I’d like to walk you through a real case that demonstrates the full process of identifying a shoe model from a shoeprint.I hope it will be helpful to professionals working in the field of footwear evidence.

This is a three-dimensional shoeprint collected using plaster casting. The tread patterns on the plaster sample are overlapping, making it difficult to distinguish how many individual shoeprints are present, their direction, and details such as the forefoot and heel.

From the tread pattern shape, it can be preliminarily judged that the shoe might be a hiking boot.

The heel is typically around 10 centimeters wide. Using the measurement tool in the software EverASM, we measure the distance between the outer edges of the heel tread patterns. After multipletests, we are able to identify the heel position in the image. 

Once the heel position is located, the next step is to determine the full position of the shoeprint. By analyzing the direction of the tread patterns, we can infer the orientation of the shoe and locate the edge patterns, which ultimately leads us to the heel's exact position. With the heel identified, we can then estimate the overall position of the shoe.

Based on the visible tread features in the image, we sketch out the clearly recognizable patterns. Any unclear orambiguous patterns should be left out at this stage, as they may negatively affect the retrieval results.

As shown in the image below, simply outlining part of the tread pattern is sufficient. The system can quickly match the shoe model in the database using just a small number of tread features.

The retrieval results are shown below. The second result is the shoe model we were looking for. The results are ranked based on the degree of feature match.

Through detailed comparison of the outsole tread, we can confirm that the shoeprint was indeed made by a shoe with this tread pattern. Tread pattern comparison can be conducted not only through graphical matching but also by analyzing length, area, and the spacing between patterns. Additionally, overlay comparison methods can also be used to verify the match.

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In the software EverASM, we searched for all the shoes associated with this outsole tread pattern and found a total of five different shoe models. Once the matching shoe is identified, investigators can use surveillance videos or other methods to track down suspects.

The layout of outsole tread patterns follows certain rules, and these patterns can reveal a lot of important information:

1. The distance between tread patterns along the edge of the sole can indicate the width of the heel and forefoot.

2. The arrangement of the patterns can help determine the direction the toe is pointing.

3. The shape of the tread patterns can suggest the intended use of the shoe.

4. Logos or markings on the sole can help identify the shoe brand.

Using a shoeprint at a crime scene to trace back to the shoe that made it is just a small step in solving a case. We sincerely hope that through our modest contribution, we can help bring new direction and opportunities to criminal investigations.

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