Casts and Impressions

Chapter 16: Casts and Impressions

Student Learning Objectives

Forensic Science: Fundamentals and Investigations, 2nd ed., Bertino & Bertino, 2015

At the conclusion of this chapter, the student should be able to:

General Information on Impressions

_____ 1. Discuss the forensic significance of impressions found at a crime scene.

_____ 2. Distinguish between latent, patent, and plastic impressions.

_____ 3. Describe why most impression evidence is considered to be class evidence.

_____ 4. Describe under what conditions impression evidence would be considered individual evidence?

Foot and Shoe Impression Evidence

_____ 5. Elaborate on how foot or shoe impression evidence can provide clues about the crime scene:

a. entrances and exits from areas

b. the number of people at the crime scene

c. evidence of confrontations

d. evidence of injuries

_____6. Elaborate on how foot or shoe impression evidence can provide clues about a person's:

a. height

b. weight

c. injuries or physical limitations

_____7. Describe the limitations of trying to relate foot size to height for:

a. children

b. teenagers

c. adults

_____8. Explain how examining a foot or shoe impression can provide evidence of a person's gait by examining:

a. length of the stride

b. where pressure is exerted

c. shape of the impression

_____9. Describe wear patterns and other evidence on shoes that could be used to help identify a particular person.

_____10. Discuss the importance of photographing a foot or shoe print before trying to lift a latent print or make a cast.

_____11. Explain the purpose of dusting latent prints prior to attempting to lift the print.

_____12. Describe how electrostatic dusting of foot or shoeprints helps to lift a print.

_____13. Explain how the use of luminol can help identify an area of latent blood smears.

_____14. Describe an advantage of using either electrostatic or gel lifting methods to reveal latent prints over using powders and lifting tape.

_____ 15. Compare and contrast gel lifting a latent footprint with lifting a fingerprint using tape.

Casting Foot Impressions

_____16. Compare and contrast casting an impression of shoe or footprint and lifting a fingerprint.

_____17. Explain the role of spraying hair spray prior to casting an impression.

_____18. Explain the purpose of adding twigs to the impression.

_____19. Describe how to cast an impression in sand using plaster of Paris.

_____20. Compare and contrast the use of dental stone to the use of plaster of Paris to cast impressions in snow.

Tire Impressions and Tread

_____21. Explain how tire evidence found at a crime scene can provide clues to:

a. the type of car that left the tire evidence

b. the direction of travel

c. when or if a car applied the brakes

_____22. List examples of how tires can leave plastic impressions at a crime scene.

_____23. Distinguish between track width and the car's wheelbase.

_____24. Explain how to measure the

a. track width

b. wheelbase of a vehicle

_____25. Explain how to measure the turning diameter of a car.

_____26. Compare track width, wheelbase, and turning diameter with data on a suspect's car to determine if the data are consistent with the crime-scene evidence.

_____ 27. Describe different physical features of tire treads that help to identify a particular model of tire. Include in your answer:

ridges
grooves
measurements of ridges and grooves
number of ridges and grooves
angle of ridges and grooves

_____ 28. Describe wear patterns on tires that would help to identify a specific car. Include in your answer:

a. underinflated tires

b. worn tires

c. damaged tire (s)

_____29. Provide an example of how tire impression evidence obtained from the crime scene can lead to the identification of a car.

_____ 30. Distinguish between a tire skid and a tire yaw in terms of:

a. direction of travel of the car when the marks were produced

b. direction of striations

c. how the marks were produced

_____31. State the significance of identifying tire scrub marks at an accident scene.

_____32. Describe an example of how skid marks left at crime scene can help determine who is at fault in a collision.

_____ 33.Describe how the following can provide evidence of the direction of travel of a vehicle:

a. changes to surrounding vegetation

b. pattern of debris on the road

c. splash pattern formed as a vehicle moves through liquids

d. transfer patters of oil or liquids in the road

e. tire marks found in the road

_____ 34. Describe how tire marks left at a crime scene can help the crime scene investigators recreate the accident.

_____ 35. Analyze the tire marks at a crime scene and record information pertaining to the vehicle that made the marks. Include in your answer:

individualized wear patterns of the tire
tire width
type of tire based on grooves and ridges in tread
wheelbase
turning diameter
direction of travel of the vehicle when the skid or yaw marks were produced
site of the collision

_____ 36. List questions that need to be addressed when reconstructing the events leading to an accident.

_____37. List four factors that need to be considered when applying the skid-to-stop formula for estimating speed at the time of impact during accident reconstruction.

_____ 38. Explain how to make a tire impression using:

a. fingerprint ink

b. plaster of Paris

Dental Impressions

_____ 39. Apply Locard’s Principle of Exchange to bite marks.

_____ 40. Relate the structure of teeth to the durability of tooth evidence.

_____ 41. Describe changes in teeth during aging that would contribute to (or detract from) the individuality of bite marks.

_____ 42. Describe how the number and type of teeth change from early development into old age.

_____ 43. Determine if a child or an adult left a bite impression by analyzing the dental impression.

_____ 44. Describe at least four factors that would contribute to the individuality of bite-mark evidence.

_____ 45. Describe different types of measurements that can be taken when analyzing dental impressions.

_____ 46. Describe how to take a dental impression from a suspect.

_____ 47. Describe how to prepare transparency overlays of the dental impression.

_____ 48. Analyze a bite mark found at a crime scene with the dental impression of a suspect.

_____49. Discuss evidence reliability of bite-mark evidence and measures currently being taken to improve its reliability.

Evidence Collection of Impression Evidence

_____50. Discuss the importance of first taking a photograph of any impression evidence.

_____51. Describe how to best photograph impression evidence.

_____52. Sequence the correct order of events when examining impression evidence:

§ lift the impression

§ cast the impression

§ photograph the impression