Trace Evidence• physical evidence found in small amounts at a crime scene• Examples ▫ hair, fiber, metals, paint, stains, inks, powders, insects, lipstick, makeup, glass particles and soil
Chemical vs Physical Property• Physical - A characteristic that does not involve a change in the identity of a substance, ▫ Examples - odor, color, boiling point, density• Chemical - A characteristic that determines how a substance will change into another substance with different physical properties ▫ Examples – rusting, combust
Metal Analysis• Bits of metal can be identified from their physical and chemical properties.• Solid metal particles are found in a loaf of bread. ▫ Were they in the flour from the manufacturer? ▫ Or were they introduced by the plaintiff for personal gain?
White Powders• Given 10 white powders• Must determine identity based on their physical and chemical properties
Makeup• In 1912, Emile Gourbin was suspected of strangling his girlfriend, Marie Latelle.• Gourbin was arrested but had an alibi.• Edmond Locard went to Gourbin’s cell and removed scrapings from under his fingernails.• The scrapings contained tissue that possibly came from Marie’s neck, but this was not provable.• Locard noticed that the tissue was coated with a pink dust• In the dust he found bismuth, magnesium, zinc oxide, and a reddish iron oxide pigment called Venetian red.• Examination of the face powder used by Marie revealed that her powder was similar in composition• In these days of mass-produced face powder, this evidence would have far less significance.• However, in 1912, because of the special preparation, it led to the confession of Gourbin.
Inks or dyes• Chromatography ▫ Stationary ▫ Mobile ▫ Chromatograph• Used to separate inks or dyes
Paint• Paint can be used as evidence in hit-and-run cases.• New Cars – 4 layers of paint ▫ Primer – corrosion protection ▫ Primer ▫ Base coat ▫ Clear coat – protection, appearance, gloss• Kind of car ▫ Make ▫ Model ▫ YearHouse Paint ▫ Jimmy or toolArt Forgery ▫ Verify or refute authenticity