Other Impression Evidence

Question 1

What is impression evidence?

Answer 1

• a texture or pattern left behind as a result of a contact/applied force
• involves a donor and recipient suface
• major focus on shoe prints and tire treads

Question 2

How is footwear impressions used in criminal investigations?

Answer 2

• footwear is the preferred term - refers to impressions made by the heel or sole of the footwear
• most people have footwear on when they commit a crime
• can be helpful but difficult to locate

Question 3

What information can be obtained from footwear?

Answer 3

• can indicate type, manufacturer, model and often exact size of the footwear
• if enough unique characteristics are present - footwear examiners believe that a pattern can be matched to a particular shoe, boot or sandal

Question 4

What can impressions indicate?

Answer 4

• route taken into and away from the crime scene
• certain activities that took place during the crime scene
• the number of people that were at the scene

Question 5

What happens when footwear touches the ground?

Answer 5

1. static electricity charge can be applied to the impression if the shoe is clean and dry
2. if the surface is soft or pliable, pressure exerted by the footwear will cause the surface to deform and take on the contours of the surface of the footwear
3. if the surface is dirt or snow, the impression may be long lasting
4. if the surface is grass or carpet, the impression may be transitory

Question 6

What is the major issue with finding footwear evidence?

Answer 6

• requires systematic searches
• have to develop strategies based on likely locations
• have to use oblique lighting techniques

Question 7

What are important considerations for footwear evidence?

Answer 7

• preserve/reproduce impressions for later examination at crime lab
• photographing remains a critical step (include scale, various angles, lighting techniques used to improve visualization)
• photographs should be considered a “plan b”
• if print is easily removable it should be brought back to the lab for comparison

Question 8

What are lifting impressions?

Answer 8

a lifting material is placed over the entire impression, rolled down and print is lifted off the surface

Question 9

What are casting impressions?

Answer 9

• uses dental stone to show greater detail
• poured into impression

Question 10

What do they use to lift prints out of the snow?

Answer 10

three coats of snow print wax is used before dental stone is poured in

Question 11

What can bloody footprints be enhanced by?

Answer 11

amido black or coomassie blue

Question 12

What do you need to compare impressions?

Answer 12

1. need a suspect item
2. test impressions may be necessary

Question 13

What does SICAR stand for?

Answer 13

shoe print image capture and retrieval

Question 14

What is SICAR

Answer 14

incorporates multiple databases to search known and unknown footwear files for comparison

Question 15

What is tire impression evidence?

Answer 15

• is the most effective way of positively linking a motor vehicle that has been at a crime scene with some degree of certainty
• casting is more often used with tire treads as they often cannot be directly lifted and brought to a lab

Question 16

What other tire evidence can be used?

Answer 16

• wheelbase and tire tread stance measurements can be taken from the tire impression