top of page
  • Writer's pictureD. P. Lyle

Criminal Mischief: Episode #53: Forensic Science For Crime Writers: Trace Evidence



SHOW NOTES:


Locard Exchange Principle


Evidence is Class or Individualizing

Evidence is Associative—connects someone to an object, a location, or another person


Types of Trace Evidence


Hair

Structure:

Medulla:

None, Continuous, Interrupted, Fragmented

Humans: None or fragmented

Thickness: Humans 1/3

Cortex: Largest part in humans

Contains pigment

Contains air pockets and ovoid bodies

Cuticle: Like fish scales

Coronal-crown-like—rare in humans

Spinous—petal-like—cats but not humans

Imbricate—flat—found in humans

Race/Sex/Age—difficult/impossible to determine

Site of Origin

Manner of Removal

Chemical Analysis

DNA—Nuclear vs Mitochondrial

Snowball The Cat Case

Shirley Duguay-victim

Douglas Beamish—perpetrator




Fibers


Classification:

Natural: cotton, wool, silk, hemp, etc.

Manufactured: from cotton or wood-Rayon, acetate

Synthetic: polymers—nylon, polyester

Wayne Williams Atlanta Child Killer Case

Examination: diameter/shape/color/shine/crimps/curls’ =

Refractive Index

Birefringence


Glass


Physical Exam: color/thickness/shape/pattern/opacity

Optical: transmit/reflect/refract

Chemical: boron/lead/pigments

Fracture Patterns



Glass Gunshot Fracture Patterns



Paint


Basic Parts: binders/pigments/extenders/modifiers

Cars: Electroplate Primer/Primer/Basecoat/Clear coat

Layers and repainting

Fracture Patterns


Soil/Plants

Place of origin

DNA


LINKS:



Fiber Evidence and the Wayne Williams Trial (Conclusion):


56 views0 comments

Comments


bottom of page