Week 4 - Positive Identification Flashcards
DNA
most conclusive way to identify
unique
need comparison DNA - from parents or siblings
types of dna
nuclear - almost all cells, from both parents
mitochondrial - from mother
problem with dna
parents who have two children that are missing - cannot differentiate between them
only way is if the child had children themselves
sources of dna - live person
nuclear - any nucleated cells - white blood cells, buccal smear, hair follicle
mtDNA - all above and hair shaft
bone marrow transplant - bloods dna will be different
sources of DNA - dead person
fresh body - blood, tissue, hair root
decomposed or skeletonized - bone marrow, teeth (dentine under enamel)
mtDNA - hair shafts
DNA comparison
unknown body gives DNA profile
compare DNA from body with premorten record of tentative ID person
DNA databank
certain offenders - rape, murder
finger prick or buccal swab
DNA taken in investigation not used in bank - second sample taken after - investigation samples destroyed (fingerprints not unless asked)
Other premortem dna
most women have DNA on record - pap smears
positive ID
can only be one person
done after tentative ID to confirm
methods of positive ID
Visual identification, fingerprints, dental records, x-rays, medical x-rays, dna, video superimposition, circumstantial
visual identification
most common, least scientific
family and friends
only used with fresh bodies unless there is a specific feature
fingerprints
old technique
unique
environmentally determined in utero
fingerprints at scene
latent prints
individualization - its your fingerprint
identification - its A fingerprint
three principles of fingerprints
individual characteristics are unique
unchanged throughout life
ridge patterns can be classified
what are prints made from
oils and sweat on skin
fingerprint individualization
examination of minutiae ridge characteristics - 150 per print
suspect print may be partial
no specific number of characteristics needed
officer making final say is subjective
levels of detail
pattern - whorl, arch, loop (classification)
minutiae - fine lines on print used for comparison
sweat pores within minutiae
quality depends on - surface, sweat, recovery time, technique used
problems with fingerprints
must have premortem record
can get prints from home - but difficult
decomposing remains and prints
if skin comes off - wear as glove
fingers can be rehydrated
dental records and x-rays
considered unique
differences in wear, rotation, root shape, fillings, extractions
used as signature in old days
dental evidence
compare premortum with postmortum record
may not be accurate because teeth can fall out..
teeth preserve well
problems with dental evidence
need premortum records
no centralized database
dentist dont keep records forever
medical x-rays
broken bones, fracture records, healing patterns
implanted devices - serial numbers
sinus shape is unique
medical records
written details, height, weight, surgeries, scars
video superimposition
match photo of tentative ID to skull
done by anthropologists
angle must be identical
easier to eliminate than ID
circumstantial
may be only method available
if a male, age 70, 150cm tall found dead in home, and apartment is owned by someone of this description, its likely him
circumstantial ID and population
if 4 men shared the house - different
closed population - one child on plane, plane crash, child bones found
white man in africa in 1800s
ID of children
difficult
little or no dental work, x-rays
small bones - not yet ossified
easily scattered and lost
sex - not until puberty, age - range, height - grow in spurts
medical cause of death
trauma, disease, or event that resulted in death
physiological process
stabbed - blood loss
strangled - asphyxiation
mode of death
instrument used
knife, rope
ways to discover cause of death
autopsy, history of death, witness statements, medical records, scene
clinical/hospital autopsy
confirms diagnoses, presence and extent of disease, medical conditions, did treatment work
forensic autopsy
cause of death, manner of death
three parts of autopsy
external exam
internal exam
toxicology
external autopsy
overview of body, clothing, biological profile, under fingernails, classify injuries if they match clothes, type of injury
internal autopsy
examine organs
digestive tract - medication
microscopic examination
toxicology
blood, urine, bile, stomach contents
blood - several areas due to postmortem redistribution of drugs
wound interpretation
description - soft or hard tissue
measure
shape - of weapon
type
size, depth, hilt mark
incised trauma
sharp force
stab - deeper
cut - longer
blunt force trauma
contusion - bruise
laceration - open wound, broken skin, tissue bridges
non sharp - bat
wound details
angle - weapon path
defence wounds
same weapon can have different wounds
manner of death
homicide, suicide, accidental, natural, undetermined
wound characteristics and manner of death
accident - mode near
suicide - weapon to hand
location of wounds - can victim reach
knife - suicide vs homicide
suicide - hesitation marks, single fatal wound, wounds reachable
homicide - many fatal wounds, out of reach, defence wounds
psychology of attack
frenzied, tentative, height of perp, position (awake or asleep), strength (wound severity)
other specialists involved
forensic anthropologist - bone trauma, exit/entry wounds
firearm specialist - match marks to weapon
where did they die?
moved - homicide to get rid of body, tampering with a body, compassion to disguise dignity
What is the difference between a coroner and a medical examiner?
Coroners can be elected officials without medical training, whereas medical examiners are physicians and board-certified forensic pathologists.
What is the primary role of a forensic pathologist?
To investigate suspicious deaths by determining the cause, manner, and time of death.
conduct autopsies
work in me or coroner office
What is involved in a scene investigation by a forensic pathologist?
Documenting and photographing the scene, identifying injuries, collecting evidence, and making a preliminary reconstruction of events based on blood splatter, weapon recovery, and movements.
What signs may indicate poisoning?
Cherry-red discoloration for carbon monoxide poisoning, pink skin for cyanide, and corrosion around lips for acid ingestion.
What are the types of asphyxia?
Carbon monoxide poisoning, hanging, strangulation, and smothering.
How can the range of fire be determined in a gunshot wound?
By analyzing powder residue and the appearance of the wound.
How can drugs contribute to death?
Drugs can cause death directly or impair judgment, leading to accidents or violence.
What part of the skin determines fingerprint patterns?
The shape of the dermal papillae at the boundary between the epidermis and dermis.
What defines a loop fingerprint pattern?
ridge enters from one size, exit from same size
one delta, core
unlar - pinkie
radial -thumb
What characterizes a whorl fingerprint pattern?
Whorls are circular or spiral ridge patterns with two deltas.
plain, central pocket, double loop, accidental
What defines an arch fingerprint pattern?
Arches lack type lines, deltas, or cores, and ridges enter from one side and exit from the other.
plain, tented
What does the ACE-V process stand for in fingerprint analysis?
Analysis: Identify distortions and determine if the fingerprint is usable for comparison.
Comparison: Compare fingerprint to a known print at three levels:
General ridge flow.
Ridge characteristics (minutiae).
Finer details (ridge pores, creases, scars).
Evaluation: Conclude identification (same source), exclusion (different source), or inconclusive.
Verification: A second examiner independently verifies the result.
primary classification in prints
each finger is paired
whorls given a value for each pair, starting at 16 then half
1 is added to numerator and denominator
What is AFIS?
Automated Fingerprint Identification System
AFIS scans and converts fingerprints into digital data focusing on minutiae, and compares them to database entries. Human experts make the final verification.
What is Livescan?
An inkless, digital system that captures fingerprints and palm prints and immediately enters them into AFIS.
What are the three types of fingerprints?
Visible prints: Made when a surface is touched after contact with colored material (e.g., blood, paint).
Plastic prints: Ridge impressions left on soft materials (e.g., putty, wax).
Latent prints: Invisible to the naked eye, formed by perspiration or oils on the ridges.
How are latent fingerprints located on different surfaces?
Hard and non-absorbent surfaces (glass, tile): Developed with powder or superglue.
Soft and porous surfaces (paper, cloth): Developed using chemicals.
What are common techniques for detecting latent fingerprints?
Powder: Aluminum for dark surfaces, carbon for light surfaces.
Superglue fuming: Forms a visible white print.
Chemical methods: Ninhydrin reacts with amino acids.
RUVIS: Uses ultraviolet light to detect prints.
What is digital imaging in fingerprint enhancement?
Converts fingerprints into digital files for analysis. Techniques like contrast adjustment and spatial filtering help make prints clearer.
describe iodine fuming, ninhydrin, physical developer, superglue fuming
Iodine sublimates into vapor when heated, interacting with oils or moisture in a latent print.
Ninhydrin reacts with amino acids in perspiration, turning the print purple-blue.
physical developer - A silver nitrate-based chemical used to develop prints on porous surfaces, especially ones that have been wet.
Superglue vapor interacts with fingerprint residue to produce a white print. It is used on nonporous surfaces and is ideal for enclosed spaces.
