Chapter 12 – Trace Elements

Chapter 12 - HWC What are the two properties of a paint sample that can be used to match two samples? (Q.2) What is unique about hair that makes it a good piece of evidence? (Q.3) Name the two “secrets” that hair samples can reveal. (Q.7) Name TWO of the four physical properties of a fibre that can be distinguished when being examined.

List the types of trace evidence given in the first paragraph List the types of trace evidence given in the first paragraph. Come up with three more of your own. Hairs, fibres, particles of dust or soil, plant debris, paint flakes and other microscopic evidence. Others???? Gunshot residue, glass, explosive residue, vehicle skid marks, blood

2. Describe the TWO properties of car paint that can be analyzed to help match two samples: Shape and colour of a paint flake can be matched with the surface from which it came. 3. What unique property of hair samples make them particularly useful as evidence? They retain their structure for a long time as they are resistant to decay. 4. What role do particles of pigment in hairs play in identifying who the hair may belong to? The way in which pigment particles are shaped and distributed, as well as their exact colour can identify a hair sample as belonging to an individual.

5. How do hairs from various areas of the body differ? Head  Circular Eyebrows and eyelashes  Circular and Tapering Beard  Triangular Armpit  Oval 6. How do hairs from various races differ? Mongoloid  continuous medulla Afro-Caribbean  Denser and less evenly distributed pigment particles than Caucasian

7. Name two other “secrets” that hair samples may tell investigators: Whether or not it has been bleached or coloured Can also reveal presence of poison in the body 8. Why do man-made fibres tend to be more valuable to the forensic investigator? Each man-made fibre has different properties and identifiable characteristics. As opposed to natural fibres like cotton, which are hard to discern.

9. What FOUR properties of a fibre can be examined in the crime lab? Diameter Exact colour Distinguishing striations caused during processing Particles of agents used modify the texture during processing 10. List THREE techniques used to examine glass as a form of evidence? Can be fitted into source from which they came to prove a match Examine fractures of broken glass to determine order of events Measure for the density of two glass samples to prove likeness

11. Where might an investigator look to find dust particles on a body at a crime scene? Suspects, suspects clothing, crime scene. Soil, plant spores, pollen particles, insects, micro-organism can provide a map of the victim for suspects whereabouts. Concrete, flour, coal or brick dust can help determine a victim or suspect’s line of work.