Ch 4

Question 1

Direct Evidence

Answer 1

eyewitnesses who have, through one or more of their five senses, experienced something relative to the crime in question or its circumstances.

two broad categories: class evidence and individual evidence.

Class evidence- cannot be linked to a particular person or an object but only to a class of objects. Class evidence includes glass, paint, shoe prints, ballistics, fibers, and tool marks.

Individual Evidence- individual evidence can be linked to a person or a specific object. One of the best examples of individual evidence is fingerprints. No two people have the same fingerprints, not even identical twins. palm prints, sole prints, voice prints, bite marks, and even ear and lip prints.

Question 2

Circumstantial Evidence

Answer 2

evidence from which an inference can be drawn and which includes items such as physical evidence. For instance, we can infer that the finding of a person’s fingerprints at the scene of a crime would indicate that that person was at the crime scene at some point in time even though no one actually saw that person there.

Question 3

Physical evidence can be divided into two broad categories:

Answer 3

class evidence and individual evidence.

Question 4

Class Evidence

Answer 4

Class evidence cannot be linked to a particular person or an object but only to a class of objects. Class evidence includes glass, paint, shoe prints, ballistics, fibers, and tool marks. for example, a particular type of glass, such as a window glass, may be linked to a crime scene.

Question 5

Individual Evidence

Answer 5

individual evidence can be linked to a person or a specific object. One of the best examples of individual evidence is fingerprints, palm prints, sole prints, voice prints, bite marks, and even ear and lip prints.

new pair of shoes when first worn has class characteristics, but over time the person’s distinct walk will develop a wear pattern that is unique to that person’s shoes and the shoes will then have individual characteristics.

Question 6

Ballistics

Answer 6

the identification of firearms, bullets, cartridges, and shotgun shells.

ballistics uses the inside of the barrel (the bore, with its lands and grooves), the firing pin, the breech face in which the firing pin hole is located, the chamber, and the ejector and extractor.

Question 7

Interior ballistics

Answer 7

the functioning of firearms through the firing cycle

Question 8

Exterior Ballistics

Answer 8

the study of projectiles in flight

Question 9

FA Handling

Answer 9

should be picked up by their rough or checkered wooden portions, if possible, or any external metal portion except the trigger guard and trigger area, and promptly placed in a container or tied to a board or strong piece of cardboard.

name of the manufacturer and the serial number. These data are necessary for tracing the weapon.

Question 10

postmortem forensic science

Answer 10

the removal of spent bullets without damage to their original condition.

Be careful, a spent bullet can be ruined by digging it out with a pocketknife. Care must be taken so that the drill or cutting instrument used in this operation does not ruin identifying characteristics on a bullet by coming into contact with the softer metal.

Question 11

gunshot residue (GSR) examination

Answer 11

applying adhesive tapes to the person’s hands. These tapes are then sent to the crime laboratory where they are examined using a scanning electron microscope interfaced with an energy-dispersive X-ray.

used to search for the presence of the major components in a center-fire cartridge:

antimony sulfide,

barium nitrate,

lead styphnate,

as well as supporting metallic particles of zinc, copper, or nickel.

Question 12

Kastle-Meyer color test.

Answer 12

This test is based on the reaction with the enzymes in the blood which causes the test strip to turn a deep blue or green. These test strips are available under the trade name Hemastix and are a useful presumptive field test for blood.

Question 13

The hydrodynamics of blood drops

Answer 13

drop size increases with the distance of the fall; the tails, or pointed ends, indicate the direction of movement; and the rounded edges face the source of bleeding.

Question 14

Luminol (dont use, kills dna)

Answer 14

luminol, which produces light rather than color as it reacts with blood. After spraying the suspected area with luminol, the room is darkened, and any blood stains present produce a faint blue glow, known as luminescence.

Bluestar, is now available and can be used in place of luminol. Bluestar has the advantage that its reaction with a bloodstain can be observed without having to create complete darkness. Both of these tests are extremely sensitive and are capable of detecting bloodstains diluted up to 100,000 times.

Bluestar preferred, does not ruin DNA

Question 15

determination is whether it is of human or animal origin

Answer 15

precipitin test and gel diffusion tests

Bloodstains which have been dried for ten to fifteen years and longer may still give a positive precipitin reaction.

Question 16

Liffting Impressions

Answer 16

first photographing and then casting the impression with plaster of Paris or dental plaster.

Question 17

prints

Answer 17

Bloody fingerprints left on weapons or at the scene of a crime are called contaminated prints

plastic prints- Fingerprints are impressions that a burglar might leave behind when his or her fingers come into contact with soft glazier’s putty around the edges of a window.

Latent Prints- cannot be seen with the naked eye and need to be developed to be seen. These fingerprints are caused by the transfer of body perspiration or oils present in finger ridges that are deposited on the surface of an object.

Question 18

cyanoacrylate fuming process

Answer 18

common glue product, is heated in a covered tank and the resulting fumes settle on the fingerprint, which is now observable and photographable

Question 19

iodine fuming or ninhydrin

Answer 19

iodine fumes react with the amino acids in the print and appear purple in color when developed.

Question 20

AFIS

Answer 20

Automated Fingerprint Identification System

Question 21

Tool marks

Answer 21

investigator finds a tool that might have made an impression at the scene of the crime and attempts to match the tool visually with the impression by fitting it to the mark. This second contact of the tool to the impression ruins the evidence. Prevailing practices suggest that the best procedure is to treat any likely tool as suspect and to collect it for laboratory comparison by an expert.

Question 22

Hairs

Answer 22

typically transferred during the commission of personal crimes such as sexual assaults, physical assaults, and homicides.

A DNA analysis can be performed on hair if the root bulb is attached

In the absence of DNA analysis the crime laboratory would conduct a microscopic analysis of the hair to determine the following.

Origin

Racial Origin

Age and Sex

Forcible removal
Hair tends to exhibit variable characteristics, not only from one person to another but also within a single individual.

Hair comparison
abnormalities due to diseases or deficiencies as well as the presence of fungal and nit infections can further link a hair specimen to a particular individual.

Question 23

Fibers

Answer 23

sexual assault cases where the victim has been bound with rope, twine, or cloth-backed tape, fiber analysis is important in determining the source of these materials.

fibers such as nylon, polyesters, and acrylics. Laboratory analysis of these fibers includes the following.

Torn clothing

Microscopic examination
examination—The first step in the analysis of fibers is the microscopic examination with a comparison microscope, which is essentially two microscopes connected together side by side that allows two samples to be viewed simultaneously

Analytical techniques
The visible-light microspectrophotometer is a reliable method for analysts to compare the colors of fibers through spectral patterns.

Question 24

Glass

Answer 24

radial and concentric fractures.

Question 25

radial

Answer 25

start at the center or the point of impact and run outward in a star-shaped pattern.

The radial fractures of the first bullet stop by themselves or run to the edge of the glass. Subsequent radial fractures produced by other bullets will stop at an already present radial fracture produced by the first bullet.

Question 26

concentric fractures.

Answer 26

form concentric circular cracks in the glass around the point of impact. If a bullet perforates a pane of glass, the hole is expanded in the form of a crater on the side where the bullet exited the pane. The location where the cone-shaped crater is narrowest indicates the direction from where the bullet was fired.