ASISTM Project Forensic Investigations

Impressions

ASISTM ProjectForensic Investigations

ShoeprintsThe physical contact between the shoe and the surface results in a transfer of the individual characteristics of the shoe.

Shoes prints are often used to prove that suspect was present at a crime scene.

3-dimensional impressionsFootwear impressions are pressed into a soft surfacesuch as mud.

The impression is influenced by the weight of the person and the type of surface.

Casting a 3-dimensional impression

Photography Paul Ricketts, 2006

Sports Shoes


Boots


Lady’s shoes


Using Alginate to make an impression 1 - alginate powder

2 - pour the alginate into a plastic bag 3 - about 1/3 of a bag


4- add water 5 - squish the powder and water

6 - thoroughly mix7 - cut a small hole at a corner of the bag with scissors


8 - squeeze out the alginate onto the impression. Work quickly as alginate dries very fast.

9 - carefully pat into place

10 - the alginate changes colour when dry - carefully lift from the impression


11 - wash away as much dirt as possible

2-dimensional impressions2-dimensional impressions occur when an image of the print is left on the surface.

Some 2-dimensional impressions are highly visible – muddy footprints on a cleaned floor – while others are latent or invisible.

2-dimensional impression: Blood



Latent 2-dimensional impression: luminol

Other impressionsCasts can be taken of the impressions ofother objects. Eg, tyre tread

Tyre tread


Tyre tread on ground


References Images

• All photography by Paul Ricketts, DUIT Multimedia, the University of Western Australia.

• J. Baines is the model for the sequence of photographs showing taking a shoeprint impression using Alginate.

• Shoes supplied by J. Dook.• Graphic design of slides by Trevor Hutchison, DUIT Multimedia,

the University of Western Australia.

Documents

ASISTM Project Forensic Investigations