Criminal Inv-Chapter 4, Circumstantial Evidence Flashcards
Two kinds of proof
Direct evidence
circumstantial evidence
direct evidence
eyewitnesses who have, through one or more of their five senses, experienced something relative to the crime in question
circumstantial evidence
evidence from which an inference can be drawn and which includes items such as physical evidence. person fingerprints,
Major type of circumstantial evidence
weapons, blood, imprints or impressions, tool mark, haris, fibers, glass, paint and questioned documents
physical evidence can be divided into 2 broad categories
class individual
class evidence
cannot be linked to a particular person or an object but only to a class of objects. Includes: glass, paint, shoe prints, ballistics, fibers and tool marks
individual evidence
can be linked to a person or a specific object. Best examples is fingerprints. One individual evidence that would directly identify a person would include palm prints, sole prints, voice prints, bite mark and even ear and lip prints.
ballistics
identification of firearms, bullets. cartridges and shotgun shells
interior ballistics
refers to functioning of firearms thru the firing cycle
exterior ballistics
study of projectiles in flight.
firearms should be picked up by their rough or checkered wooden portions, if possible or any external metal portion except
trigger guard and trigger area.
gunshot residue examination (GSR)
applying adhesive tapes to person ‘s hands. Tapes then sent to crime lab where a scanning electron microscope interfaced with an energy-dispersive X-ray. The search is for presence of the major components in a center-fire cartridge:antimony sulfide, barium nitrate and lead styphnate, as well as supporting metallic particles of zinc, copper, nickel
exothermic reaction
compounds and elements are deposited on a persons hands when they fired a weapon and they undergo an intense exothermic reaction due to rapid increase in temperature followed by a sharp decrease. This supercooling phenomenon leads to a unique spheroidal formation that is generally not observed in the natural environment
relatively fresh bloodstains generally appear to be
reddish-brown in color; howeverover-time the stain can appear to be red to black, appear to be green, blue or even grayish white.
kastle-meyer color test
determination of whether or not the stain is blood is made by this test. Test is based on the reaction with the enzymes in the blood which causes the test strip to turn a deep pink color
blood test strips are available under the trade name
Hemastix, are useful presumptive field test for blood
to test whether blood was present at one time at crime scene and has since been cleaned up
luminol- produces light rather than color as it reacts with blood. After spraying, the room is darkened and any blood stains present produce a faint blue glow, known as luminescence
A new product to detect blood, trade mark name
Bluestar-it has the advantage that its reaction with bloodstain can be observed without having to create darkness. Both Bluestar and luminol are extremely sensitive and are capable of detecting bloodstains diluted up to 100,000 timess
precipitin test
to determine whether the blood is human or animal.
test are based on reaction when animals are injected with human blood. Injection causes antibodies to form that react with human blood to neutralize its presence.
another precipitin test
gel diffusion- test takes advantage of the fact that antibodies and antigens diffuse or move toward one another on a plate coated with a gel medium made from polymer called Agar. if the blood is human, a line of precipitation forms wher the antigen and antibodies meet. Gel diffusion test is very sensitive and requires only a small amount of blood for testing. Bloodstains which have been dried for 10 to 15 years and longer may still give a positive precipitin reaction.
contaminated prints
bloody fingerprints left on weapons or at scene of a crime.
plastic prints
fingerprints are imipression that a burglar might leave behind when fingers come into contact with soft glaziers puty around the edges of a window
imprints
markings left on a surface by protruding parts of a person or vehicle.
latent prints
cannot be seen with the naked eye and need to be developed to be seen. fingerprints are caused by the transfer of body perspiration or oils present in finger ridges that are deposited on surface of object.
