Exam 1 Flashcards
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What is Forensic Science
The application of scientific principles/techniques to a legal investigation
Identifying Specimens based on what?
Class characteristics
Collected Samples @ a crime scene
Unknown, Questioned, and Known
Ways comparison can be done?
Searching a database or taking a known sample
Class characteristics
Blood, Saliva, Fiber
Important technique to be accepted into forensic field
Accepted by scientists in the field, and technique is admissible in court
Legal Acceptance (United States)
Frye or Daubert
Kansas Legal Acceptance
Adopted Daubert in 2014
Validation 3 R’s
(R)eliable
(R)obust
(R)epeatable
Scientific Acceptance
1.Been Validated
2. Method accepted in the field?
3. Standards in the field? (Negative and Positive controls)
Securing the scene
Perimeter
Permitted Authorization
Log of who has been in and out of the crime scene
PPE
Protect investigators from bodily fluids and prevent contamination of evidence
Types of connections
Victim-to-perpetrator
victim-to-scene
perpetrator-to-scene
Victim-to-perpetrator
Victims blood on a suspects clothes
Victim-to-scene
Fiber from sheet found in victim in dumpster
Perpetrator-to-scene
Mud on shoes from riverbanks where dead body is found
Locard Exchange Principle
Cross-transfer of evidence occurs when a perpetrator has any physical contact w/ another person or object
Modus Operandi
Set of characteristics consistent w/ multiple crimes committed by the same person.
Helps establish a case-to-case linkage
Outdoor scenes
Grid or line patterns of searching
Indoor Scene
benefit from climate control.
More places for things to be hidden
Search for Biological Evidence
Alternative Light Source (ALS)
Chemiluminescent enhancement reagents
Luminol
Enhances blood
Biological Specimens
Bleach and plant peroxidases
Crime Scene Photography
Make sure proper setting are used
Need to have reference items for size
3 types of pictures: Overall, Midrange, and Close-up
Collecting Evidence
Documented
Smaller items= crime lab
Larger items=document
Way evidence is packaged depends on its physical properties
Bloodstain Patterns
Needs to thoroughly document pattern of strain
Could play a role in reconstruction
Trace Evidence
Hair and Fiber
Wet Evidence
Needs to be air-dried prior to collection
Failure to do so could result in growing bacteria
Control Samples
Sample from an unstained area near the stain should be used as a control
Evidence Marking
Clearly Identifiable
accomplished by being initiated, dated, and itemized
When opened, it should be in a different spot and dated/initialed
Collecting Blood
Wet- Swab, FTA paper
Dry- Swab, cutting, scraping, and lifting
Additional Sources of Biological Evidence
Victim
Relatives
Others in the area
Crime Scene Reconstruction
Looks at the morphology, sequence, and distribution of bloodstains
May reveal sequence of events, location, intensity and more
Basics of Blood
8% of body weight
Cellular- blood cells and platelets
Liquid- Plasma
Bloodstain formation
Size, number, and intensity of the bloodstream can vary
Viscosity, surface tension, cohesive force, and gravity
How does a bloodstain form
As the volume of blood increases, the drop stretches down
How does surface alter bloodstain pattern
Texture of the surface alters the appearance of the drop
Documentation of bloodstain
Sketches, photos, and videos
Photo Parallel to surface to avoid distortion
Spatter stain analysis
Velocity and directionality influence the pattern of bloodstains
Can be used to determine area of origin
SWGSTAIN definition
A bloodstain resulting from a blood drop dispersed though the air due to an external force applied to a source of liquid blood
Blood Stain size
Droplet size=force that is applied
force increases=surface tension reduces=smaller droplet
Low impact drop
> 4 mm in diameter
dripping from a wound
Detection of Blood stain
if deposited at an angle between 0-90 degrees you can calculate the direction of the blood @ the time of depositing
Medium Impact drop
1-4 mm in diameter
beating/stabbing
High Impact drop
<1 mm in diameter
gunshot
Parent Stain
spatter stain is an elongated ellipse
Satellite Stain
Smaller blood stains near the parent stain
Spine
portion of the blood stain that is the pointed edge away from the parent stain
Points towards the direction of travel for the blood stains
90 degree blood stain
circle
50 degree blood stain
circular but has satellite stains
20 degree blood stain
has a small spine
10 degree blood stain
dripping blood stain with a spine
Formula for determining the angle of impact
sin a(= (w/l)
Types of bloodstain patterns
passive, transfer, and projected
Passive Bloodstains
Formed by bleeding
a drip stain
drip trail
pod patterns
Transfer bloodstains
resulting from contact between a blood-bearing surface and another surface
Swipe or wipe
can tell size, shape, and pattern
Projected Bloodstains
Resulting from the transfer of blood from a blood bearing surface onto another surface
Impact and arterial
result of a weapon use in the assault/homicide
Biological sample why it varies
the type of crime
amount of time between the crime and discovery of evidence
the location of the crime
Biological evidence
bodily fluids and tissues
Baseball Bat
Handle
Skin cells, sweat, blood, tissue
Bite mark
Skin surface
Saliva
Sources of DNA profiling
Blood- 86.1
Semen-92.1
Saliva- 37.2
Cigarette Butts- 73.5
Chewing gum- 71.2
Hair- 18.1
Transferred- 12.4
Bases of DNA
A,T,C,G
In forensics terms, DNA means
Nuclear DNA
Cell Types
Sex Cells- Sperm and Oocytes
Somatic Cells- Other types
Sex Cells
Gametes- Spermatozoa and Ova
each gamete is a haploid: single set of chromosomes; 22 autosomes
Somatic Cells
Most other cells (non-sex) in the body
These are diploid cells 46 chromosomes
Cells without nuclei
Nulliploid: red blood cells and platelets
Cells with more than 2 chromosomes
polyploid: regenerating cells of the liver
Blood consists of
plasma, red blood cells (erythrocytes), white blood cells (leukocytes), and platelets
Transcellular Fluids
Saliva, seminal fluids, and vaginal secretions
found in extracellular fluid
Ex- Buccal cells in saliva
Extracellular Nucleic Acids
Non-compartmentalized fluids like plasma
Skin evidence
Fingerprints and Shed skin
Latent Fingerprints
Arch, Loop, and Whorl
Skin biology
consists of different layers (distal to proximal)
Epidermis
outer layer of skin; contains melanin
Dermis
Middle layer of skin; contains hair follicles, sweat glands, blood, lymph vessels, and nerves
Subcutaneous layer
Deepest layer; contains collagen networks and adipose tissue
Epidermal layers
Basal, spinous, granular, and cornified
Hair characteristics
Color, species, identification, and type
Hair shaft
keratinized cylindrical structure
Medulla
Center
Cortex
Middle Section; contains pigment
Cuticle
Outer layer; overlapping cells that protect the cortex and medulla
Keratin
Fibrous structure protein
Used to protect epithelial cells from damage
Shell of a turtle
claws of reptiles
Hair growth phases
Anagen, Catagen, and Telogen
Anagen Phase
hair growth occurs
Catagen Phase
begins when cell death occurs
Telogen phase
stage of rest
hair for DNA analysis
root needs to be present
Bone anatomy
206 bones in adult
Long shaft bone 3 parts
Outer layer of cortical (compact) bone: solid and strong
Marrow Cavity: Formed inside the bone; filled with bone marrow
Epiphysis: ends of bone; made up of spongy bone
Bones contain cells inside of an _____
Extra cellular matrix
Protects the fibrous proteins (organic)
a hard matrix (inorganic)
Inorganic matrix consists of
calcium and phosphate
Organic Matrix consists of
collagens (insoluble fibrous proteins)
Developing bones contain
osteoprogenitor cells; produce osteoblasts and osteoclasts
Osteoblasts
regulate calcifications of the bone matrix
Osteoclasts
dissolve and recycle the bone matrix; contains lots of nuclei
Anatomy of teeth
Organic and inorganic matrix
Teeth for DNA analysis
Use the root portion of the tooth
