Forensic Science - Footmarks

What are the 3 types of footmark?

• Visible.

• Latent.

• Plastic.

What is a visible footprint?

• Prints you can see with the naked eye.

• When someone steps in mud, blood, paint and treads it around a crime scene.

• Can also be if someone stepped in dust and left a negative print.

• Doesn’t need chemicals to see them.

What are latent footprints?

• Not visible to the naked eye without special techniques.

• They’re made from sweat, oils or skin sells on the sole of the shoe.

• They require enhancement (powders, ninhydrin, UV).

• E.g. footprint on paper enhanced with ninhydrin to show sweat marks.

What are plastic footprints?

• 3d, leaves an impression in a soft material.

• Occur when someone steps on mud, sand, clay.

• They are visible.

What is ESLA?

• Electrostatic lifting apparatus.

• A special plastic film is placed over a dusty/powdery footprint.

• The film is given electrostatic charge which makes the dust cling to it.

• The print is now lifted onto the film for analysis.

What is a gelatine lift?

• A gelatine sheet is laid over the footprint gently.

• It needs to make full contact with the print without destroying any of it.

• It is then peeled off slowly and preserved to be analysed.

• It is used for lifting dirt or dust impression footprints. 

Explain the process of casting footwear impressions.

• A powder (dental stone, plaster) is mixed with water to create a paste.

• The footprint needs to be sealed into the sand/mud with a fixative.

• It is poured onto the footprint impression and then it needs to set.

• A cast is made and can be examined.

What is classification?

The examination of class characteristics such as:

• Size.

• Shape.

• Tread.

• Design.

What is individualisation?

Looking for unique features such as:

• Cuts.

• Tears.

• Wear.

• Pinholes.

What are toolmarks?

A negative impression left when a tool is pressed into a material.

What is a striation?

A fine, linear mark left on a surface when a tool scrapes across it. They reflect the tool’s unique microscopic characteristics/#.

What are individual characteristics of a tool?

Marks made during manufacture of a tool. Frequent use of the tool may cause scratches on it or break part of it, giving them individual characteristics. They are unique to a tool.

What are class characteristics of a tool?

The size and shape of the tool.

Name 2 methods that can be used to analyse toolmarks.

• Comparison microscope.

• Casting.

How can you examine toolmarks using a comparison microscope?

• The toolmark found at the crime scene is collected.

• The suspect tool is used to make test marks on a similar material.

• Each of these samples are placed under a side of the microscope.

• The examiner then analyses both samples to see if they’re a math by looking at the striations.

What is the ACE-V method? Briefly explain each stage.

• Analysis - assessment of the mark.

• Comparison - comparison of friction ridge details in 2 marks / prints, determining agreement or disagreement.

• Evaluation - conclusion based on the examination.

• Verification - independent examination by another examiner reaching same conclusion.