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.
latent fingerprints
on porous surfaces such as paper are developed in the lab thru an iodine fuming or ninhydrin process. Iodine fumes react with the amino acids in the print and appear purple in color when developed.
cyanoacrylate fuming process
prints left on smooth, slippery surfaces such as plastic bags, which are resistant to the dusting process. Cyanoacrylate a common glue product, is heated in a covered tank and the resulting fumes settle on the fingerprints, which is now observable and photographed
Automated Fingerprint Identification System-AFIS
fingerprints to be captured electronically. Prints is electronically sent to FBI database, which contains 55 million sets of prints. the Criminal ten-print processing time from forty-five days to less than two hours
DNA analysis can be performed on hair if
root bulb is attached
without DNA analysis the crime lab would conduct a microscopic analysis of the hair to determine the following
orgin- what part of body
racial origin-Cross-sectional analysis of caucasian hair demonstrates that it is oval to round in shape while hair from a person of African decent is flat to oval in shape. General observations and there is much overlap between the races, which makes it difficult
Age an sex- cannot be determined with any degree of certainty, exeption of infrant hair
Forcible removal- absence of adhering tissue to the bulbous-shape root is more likely to be the result of naromally falling off body than forcible
hair comparison-the most common request. Not yet possible to individualize a human hair to any single person thru its structural characteristics.
fibers
often a key items of evidence where cross-transfer of fibers may occur.
fibers classified into two broad groups
natural- cotton, wool
manufactured- synthetic, nylon, polyesters and acrylics.
lab analysis of these fibers includes
torn clothing
micropscopic examination
analytical technigques- visible light microspectrophotometer, reliable method for analysts to compare the colors of fibers thru spectral patternss. limited by sample size: fiber as small 1 millimeter
two types of fractured glass
radial fractures- start at center or point of impact and run outward in a star-shaped pattern
concentric fracture- concentric circular cracks in the glass around point of impact
fracture match
collected glass found on suspect clothing or hit an run victims clothingcan be compared to determine if the splinter will fill the void.
pain evidence is usually found in form of
smears or chips
chips tend to be more useful, showing conclusively that paint came from a
specific location if the chips are large enough and edges can be fitted together. However, only class characteristics can be determined by paint analysis
paint and protective coatings
lacquer, enamel, varnish can be identified by physical and chemical properties.
paint and coatings physical characteristics
color, layering, weathering, texture are useful in characterizing this type of evidence. Chemical properties such as solubility and composition can indicate the type of paint and identify the pigmentation and fillers used in manufacturing.
questioned document
checks, suicide notes, written or typed documents
hydrodynamics of blood drops and splashes
drop size increases with distance of the fall; the tails, or pointed ends, indicate the direction of movement and round edges face the source of bleeding
