Intro to Forensics -- Chapter 14: Metals, Paints and Soil

what metal items found at crime scenes are commonly examined?

bullets, copper wires, pipes

trace elements

many manufactured products and natural materials contain small amounts, unique to the sample

what items use the comparison of trace elements to determine the possibility of a common source?

glass, paint, soil, fibers, metallic objects

elemental analysis

the experimental measurement of the percent composition of elements in a compound

emission spectroscopy

type of elemental analysis, compares what color light the sample emits

how is the emission spectrum interpreted?

it can be matched line by line

equation for specific frequency of light absorbed or emitted

E= hf

neutron activation

a procedure used to detect trace amounts of elements in samples by bombarding the sample with neutrons from a radioactive source

alpha particles

positively charged particles with about four times the mass of a hydrogen atom

gamma rays

electromagnetic waves with the shortest wavelengths and highest frequencies

beta particles

a negatively charged particle emitted from the nucleus of an atom during radioactive decay

how do you identify the radioactive isotope using neutron activation?

by measuring the energy of the gamma rays emitted as radioactivity

what types of case are paint samples important to?

hit-and-run, burglaries

what are the most common automobile paint coats?

electrocoat primer, primersurfacer, basecoat, and clearcoat.

paint solvent

makes the compound a liquid, evaporates while drying, will not be present in microscopic analysis

paint binder

helps pigment adhere to the surface

pigment

a colored chemical compound that absorbs light

what methods are most commonly used for paint analysis?

pyrolysis gas chromatography and infrared spectrophotometry

paint data query

a database that provides information on paints based on make, model, and year

how is paint collected?

paper druggist folds and glass or plastic vials

what makes soil valuable in crime scenes?

being unique to its location, easily transferable,

microscopic examination of paint

color, surface texture, number of layers, color sequence

pyrolysis gas chromatography

burns solid paint to gas, destructive

infrared spec. in relation to paint

measures each layer separately, measure of what wavelength it absorbs and how much light is absorbed

pigment examination of paint

emission spec, x-ray spec, elemental analysis

soil

an disintegrated material on or near the earth's surface

standard/reference soil samples

collected at various intervals within a 100-foot radius of the crime scene

how is soil compared?

color, texture, density, seeds, mineral particles

the emission spectrograph is used to determine the

elemental composition of a substance

paint binders can be chemically analyzed using

TLC and IR spec

if soil is found adhering to an object, the investigator should remove the soil particles from the object and send them to the laboratory

false

1 multiple choice option

the variety of coatings applied to the body of an automobile adds significant diversity to automobile paint and contributes to the forensic significance of automobile paint comparison

true

1 multiple choice option

emission spectroscopy measures the frequency of light emitted by an atom when one of its electrons moves to a higher orbital

false

1 multiple choice option

which is NOT part of the composition of paint

adhesive

3 multiple choice options

an element is selective in the frequency of light it will absorb. this selectivity is due to its

electron energy levels

what is the logical first step in soil analysis?

comparison of dried soil sample for color and texture

which property imparts paint with its most distinctive forensic characteristics?

color

the ________ properties of crystals, such as refractive index and birefringence, provide points of identification that help characterize them

optical

which coat represents the "eye appeal"?

basecoat

3 multiple choice options

it is not necessary that the collected paint from a vehicle involved in a hit-and-run accident be close to the area of the car suspected of being in contact with the victim

false

2 multiple choice options

which coating provides resistance to corrosion

electrocoat primer

the concentration of the absorbing element is directly proportional to the quantity of the light absorbed

true

3 multiple choice options

the investigator should not try to remove trace paint evidence found on a tool but package the tool for laboratory examination instead

true

2 multiple choice options

the proton and electron ________ of approximately equal mass.

are not

3 multiple choice options

an _________ spectrum shows distinct frequencies or wavelengths of light

electromagnetic spectrum

beta particles are identical to...

electrons

as an electron falls from a higher to a lower energy level, it emits...

a photon