JS 96GY: Trace evidence- Hairs, Fiber and Paint

I. Announcements, Assignments and AcknowledgementsII. Learning Objectives (Chapter 7)

a. Hair1. Describe cuticle, cortex and medulla and 3 growth phases2. Explain distinction between human vs animal hair3. List useful macro and microscopic hair features4. Explain proper collection of hair evidence5. Describe the role of DNA typing in hair comparisons

b. Fibers1. Classify fibers2. Describe the structure of a polymer3. List useful forensic properties of fiber4. Explain proper collection of fiber evidence

c. Paint1. Describe the components of paint2. Classify auto paints3. List those examinations most useful for forensic comparison of paint4. Explain proper collection of paint evidence

Assignments and AcknowledgementsCollect Assignments- Chapter summaries and extra creditReminders-

Final Exam- Monday 15 Dec 08- 0945-1200CSI Notebooks due - Weds 10 Dec 08MUSE workshops- Weds 10 Dec 08Bring hard copies of summaries this weds 10 Dec and posthandouts and powerpoints to Google group

AssignmentsPrepare Student led reviewsStudy for final examSOTEs Weds 10 Dec

Acknowledgements– Marty Blake- SFPD– Jeremiah Garrido and Larry Turner: SCCCL

Summary 1• Trace evidence includes Animal (hair), Vegetable (fiber), or Mineral

(glass, explosives, gunshot residue) – It is fragile, easily missed and/or lost.

• Hairs extend from its root in the follicle into a shaft and terminates at a tip end- Three layers of the hair, the cuticle, cortex and medulla are subjected to the most intense forensic examination - Color, length and diameter

• Morphological features distinguish human vs animals• Scale structure, medullary index and medullary shape are important• Medullary shape and the distribution, shape and color intensity of the

pigment granules present in the cortex are important forensic features.• Nuclear and mtDNA can be analyzed from hair roots and mtDNA

from hair shaft

Summary 2The quality of fiber evidence is dependent on the ability of the criminalist to

identify the origin or narrow down the number of sourcesMicroscopic comparisons of known and questioned fibers at undertaken for color

and diameter.Striations on the fiber, delustering particles and cross-sectional shape are

examined.Visible light micro-spectrophotometer and FT-IRIR spec is rapid and reliable for identifying the generic class of fibers.Paint consists of pigments and additives suspended in the binder. Auto paint is

compared under a stereoscopic microscope for color surface texture and color layer.

Pyrolysis GC and IR spec can be used to distinguish most paint binder formulations