crime scenes exam 1
what steps must the first responder take
-discover/report crime -uniformed officer responds -deal with medical emergencies -secure scene (establish perimeter) -prevent destruction of evidence (change of scene) -limit entry/exit in scene (establish enter/exit pathway) -make initial survey
trace evidence
-generic term for small, often microscopic material -collected at a crime scene is analyzed in forensic laboratories by trained forensic scientists
types of physical evidence
-individual and class characteristics
things to avoid in photos/videos
-police/equipment in shots -gaps in running video
uses of photography
-presents logical story visually
value of physical evidence
-reconstruct scene -determine if a crime actually happened -link suspect to victim/crime scene -provide investigative lead -provide facts to determine guilt or innocence -provide possible linkage to other crimes
how do you collect paint smears
-scrape at least 1/4 inch by 1/4 inch aread with clean blade -be certain to scrape all paint layers -scrape damaged area and undamaged area -package separately in envelopes, boxes, or vials
why not just use a laser
-they are monocromatic -line is too tight -too intense for human eye -can cut through steel
what are the four tests of admissibility
-whether evidence can be or has been tested by scientific methodology -Whether underlying theory or technique has been subject to peer review and published in professional literature -How reliable the results are in terms of potential error rate -General acceptance can continue to have bearing on the inquiry
how many people are required for strip searches
1 or more
types of trace evidence
Hair, fiber, paint chips, body fluids, stains, powders, explosive residue, glass particles, vegetable matter, metal particles, soil, etc.
stokes shift
When energy projected onto object, it is absorbed by the object then reemitted; energy becomes weaker
how are individual characteristics important to glass evidence
a fracture pattern can lead to a positive comparison
Categories of Trace Evidence
animal, vegetable, mineral, synthetic
what are the types of paint
architectural, automotive
how wide is each strip in a strip search
arms length on either side
comparison
ascertain whether two or more objects have a common origin
refraction
bending of light wave as it passes from one medium to another
components of architectural paint
binders, pigment, solvents
why does ALS not work on blood
blood absorbs light it does not fluoresce
where is paint encountered
burglaries and hit and run accidents
the absence of evidence ________ ; anything is evidence until ______ _________
can be evidence; it isn't
characteristics of medulla
cells arranged in varying ways that assist in species determination
what is physically examined in paint evidence
color and hue, surface texture, layer number, layer sequence, layer thickness, chip comparison
what is compared when analyzing fibers
color, diameter, type, thread count, direction of twists, dyes
CADD sketch
computer aided drafting and design ; software packages such as SmartDraw
what is the medulla layer
core area of hair; usually amorphous (shapeless); narrow in humans; can be fragmented or absent
what are the cuticle scale patterns
coronal, spinous, imbricate
how can the cortex be used to differentiate between humans and animals
cortex layer contains pigment granules in humans; pigment is in medulla in animals
what is concentric fracture
cracks that make a circle around the point of impact
what is a radial fracture
cracks that originate from point of impact and travel away
types of forensic experts
crime scene techs and photographers, fingerprints, ballistics, etc
how can the cuticle be used to differentiate between humans and animals
cuticle scales overlap smoothly in humans; are rough in animals
what are the layers of hair
cuticle, cortex, medulla
Locard Exchange Principle states that:
every time you enter an environment you leave something and pick something up
individual characteristics
properties of evidence that can be attributed to a common source with an extremely high degree of certainty ; one and only one source
class characteristics
properties of evidence that can only be associated with a group and never with a single source
uses of infrared photography
questioned documents, gunshot residue
what are the different fracture patterns of glass
radial, concentric, conchoidal
chain of custody
record of all persons who had possession of physical evidence from the time it was collected until the time it is presented in court
sources of trace evidence
scene, victim/suspect clothing, tools, weapons
Daubert v Merrell Dow Pharmaceuticals
scientific reliability,, four tests of admissibility
what is a strip search
search in lanes
what is visible with UV photography
semen, fibers, fluorescent fingerprint powder, bite marks
what makes a forensic expert
skills, certifications, ethics, peer reviewed
what is chemically examined in paint evidence
solubility, refractive index, chemical components
evidence
something legally submitted to a competent tribunal as a means of ascertaining the truth of any alleged matter of fact under investigation before it ; anything brought in legally to prove something in court
Types of search patterns
spiral, strip/line, grid, zone/quadrant
what is a spiral search
start outside and work inward
search patterns
systematic, methodical search for physical evidence
what is direct evidence
testimony directly tying defendant to crime
crime-scene investigation
the use of science and technology in determining facts in a criminal investigation
what are examples of physical characteristics of glass
thickness, color, uniformity, curvature, surface(tinting)
why include a ruler in photographs
to indicate size
examples of paint evidence in burglaries
tool marks, wet paint
what areas do you collect known scalp samples from
top, front, back, crown, sides
what is the spinous scale pattern
triangular in shape
true or false: grid searches are used in large areas
true
true or false: grid searches are used indoors and outdoors
true
how does ALS work
uses light energy from outside what can be typically seen by the naked eye
who has the spinous scale pattern
usually cats - never humans
are strip searches used indoors or outdoors
usually outdoors, commonly indoors
who has the coronal pattern
usually small rodents - not human
why does ALS use blue light
violet is too strong to distinguish things
what color is all visible light combined
white
how do you collect large pieces of glass evidence
wrap individually in paper; place in boxes
what is the coronal pattern
like a stack of paper cups
what is the imbricate scale pattern
like roofing shingles
purpose of alternate light source
locate and visualize trace evidence
how do things glow using ALS
luminescence is produced by changes in "ground state" of atom
cons of audio in videos
make erroneous or embarrassing statements
results in comparison
match, some similarities, no similarities
rectangular coordinate sketch
measure distance of an object from two fixed points at right angles to each other; usually the walls that abut each other
triangulation sketch
measure distances of an object along a straight line from two widely separated, fixed reference points
what are optical characteristics of glass
measure properties through refractive index
exploded view/cross projection sketch
method where ceiling appears like an open lid with four walls outward; used when evidence is found on walls
what is the cortex
middle and predominant layer of hair
What unit is light measured in?
nanometers
are spiral searches used frequently
no
are spiral searches for indoor or outdoor searches
outdoor
what is the cuticle
outermost layer of hair
what is the individual type of paint evidence
paint chips
what is the class type of paint evidence
paint smears
examples of paint evidence in hit and runs
paint transfer, fabric impressions
types of visual records
photography, video, infrared photography, ultraviolet photography
glass' varying composition allows it to be discriminated by what three things
physical, optical, and elemental characteristics
what microscopic features are in the cortex
pigment, color, size
how do you mark evidence
place a marker near each piece of evidence
how do you collect particles of glass evidence
place in boxes or plastic vials
what are man-made fibers made from
polymers
involves the (5 things) of physical evidence left at crime scene
preservation, processing, packaging, transportation, and documentation
third step in crime scene investigation
processing the scene
longest wavelength of visible light
700nm (red)
what steps do csi's have to take
(based on crime/agency policy) -speak to first responders (what they observed/tour scene with them) -establish plan for processing scene -maintain record
what makes evidence admissible in court
-"rules of evidence" -judge says what is admitted and who presents it -competency (witness qualifications)
chararistics of glass
-Rigid liquid made by cooling a molten mass in quick manner that avoids crystallization -found in many shapes, sizes, colors, and types -has wide variety of chemical compositions
how do you collect fibers/hairs
-bag entire item(best) -use tweezers or forceps -use fiber-lifting adhesive tape -use vacuum sweeping
fiber fracture patterns
-broken button -cut wire
how do you collect paint chips
-collect entire chip -package carefully to prevent breakage -fracture pattern is possible
characteristics of cuticle layer
-composed of transparent pigment -free, overlapping scales pointing toward tip end of hair -like the painted area of a pencil
what steps are involved in processing the scene
-conducting a search -visual record of scene -sketching the scene -collect physical evidence
how many pubic samples do you collect for known standards
10 from each area,, 50 in total
how many scalp samples do you collect for known standards
15-20 from each area,, 75 to 100 total
how many other hair samples (arms, legs, etc) do you collect for known standards
20-30 from each area
shortest wavelength of visible light
400nm (violet)
what are elemental characteristics of glass
determine chemical composition; argon plasma torch
identification
determine the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit
types of evidence
direct, circumstantial, demonstrative, physical
second step in crime scene investigation
dispatch crime scene investigation team
first step in crime scene investigation
dispatch first responder
what is a quadrant search
divide area into four quadrants and use another search pattern within each quadrant
Ultraviolet Photography
documents materials that glow under UV
what is a grid search
double strip pattern
who discovered ALS
dr. roland menzel
components of automotive paint
electrostatic primer, primer, basecoat, clearcoat
true or false: memory cards do not count as evidence
false
true or false: red is strongest but violet is most visible
false
true or false: spiral searches require multiple people
false
true or false: you can return to the crime scene if you didnt get everything
false
common applications of ALS
fingerprints, physiological fluids, fibers/hairs, flammables
what is physical evidence
found at the crime scene that ties suspect to crime
Frye v U.S
general acceptance does not equal reliability
how are class characteristics important to glass evidence
glass particles can lead to a possible comparison
pros of audio in videos
good to narrate
what is the most thorough search pattern
grid
who has the imbricate scale patterns
humans and many animals
What is demonstrative evidence?
illustrative evidence that is tangible; has objective existence
infrared photography
images formed by use of infrared light
what is conchoidal fracture
indicates the direction from which the force was applied
What is circumstantial evidence?
infers from a series of known facts so deductions can be made
