CSI - Crime Scene Investigator Impression and Pattern Evidence Questions and Answers 1 — Questions and Answers
Question 1: An investigator discovers a faint, two-dimensional dusty footwear impression on a dark-colored tile floor. Which of the following collection methods would be most effective for recovering this type of evidence?
- Gelatin lifter
- Dental stone casting
- Electrostatic dust print lifter (Correct answer)
- Adhesive lifter with fingerprint powder
Correct answer: Electrostatic dust print lifter
An electrostatic dust print lifter is the most effective method for collecting dry or dusty residue impressions. It uses an electric charge to attract and bond the dust particles to a special lifting film, preserving the delicate details of the impression with minimal disturbance.
Question 2: A three-dimensional footwear impression is found in mud at an outdoor crime scene. Before casting with dental stone, what is a critical first step in the documentation process?
- Spraying the impression with a fixative like hairspray.
- Taking examination-quality photographs at a 90-degree angle with a scale. (Correct answer)
- Removing any leaves or twigs embedded in the impression.
- Building a retaining wall around the impression.
Correct answer: Taking examination-quality photographs at a 90-degree angle with a scale.
Properly photographing impression evidence before any other collection technique is applied is a critical step. Examination-quality photographs must be taken with the camera positioned directly above (90 degrees) and parallel to the impression, including a scale, to accurately capture its size and details for later comparison.
Question 3: A forensic examiner is comparing a tool mark from a crime scene with a suspect's pry bar. The examiner notes that both the questioned mark and the test mark were made by a tool with a 1-inch flat tip. This observation relates to what type of characteristic?
- Subclass characteristics
- Individual characteristics
- Accidental characteristics
- Class characteristics (Correct answer)
Correct answer: Class characteristics
Class characteristics are measurable features or traits of a tool that are predetermined by the manufacturer's design, such as the width of a screwdriver tip or the shape of a pry bar. These features can associate a tool mark with a group of similar tools but are not unique.
Question 4: At a homicide scene, a bloody footwear impression is discovered on a light-colored linoleum floor. The impression is visible but faint. Which chemical enhancement technique is most appropriate for improving the detail of this bloody pattern for photography?
- Ninhydrin
- Amido Black (Correct answer)
- Cyanoacrylate fuming
- Luminol
Correct answer: Amido Black
Amido Black is a protein stain that reacts with proteins found in blood, staining them a dark blue-black. This enhances the contrast of visible or latent blood impressions on non-porous surfaces, making it ideal for photographing faint bloody footwear patterns. Luminol is used for detecting latent blood, not for enhancing detailed patterns.
Question 5: Which of the following describes a 'plastic' impression?
- A bloody shoeprint on a white tile floor.
- A dusty footprint on a wooden plank.
- A tire track left in soft soil or snow. (Correct answer)
- A fingerprint lifted from a glass surface.
Correct answer: A tire track left in soft soil or snow.
A plastic print is a three-dimensional impression left on a soft, malleable surface. Examples include shoe or tire tracks left in sand, mud, or snow, where the object has physically indented the surface.
Question 6: When casting a footwear impression in snow, which material is commonly sprayed into the impression first to insulate and firm it up before applying dental stone?
- Talcum powder
- Gray primer or Snow Print Wax (Correct answer)
- Potassium sulfate
- Hairspray
Correct answer: Gray primer or Snow Print Wax
Due to the fragile nature of impressions in snow and the heat generated by the curing process of dental stone, a fixative is needed. Snow Print Wax or a gray automotive primer is lightly sprayed over the impression to insulate it and prevent it from melting when the casting material is poured.
CSI - Crime Scene Investigator Impression and Pattern Evidence Questions and Answers 1
An investigator discovers a faint, two-dimensional dusty footwear impression on a dark-colored tile floor.
Which of the following collection methods would be most effective for recovering this type of evidence?