intro forensics midterm

what is forensic science

application of science to the criminal and civil laws that are enforced by police agencies in a criminal justice system

criminalistics

subcategory of forensics focused on services provided by crime lab

first major forensics lab

1932, FBI national laboratory under Hoover, offered services to entire country

first ever forensics lab

1923, LAPD by August Vollmer

an effective forensic scientist is:

-able to discover evidence using modern scientific techniques

-must be able to recognize potential value of evidence

-must be able to accurately apply testing scheme based on scientific method

Locard’s Exchange Principle

every contact leaves a trace; there is a scientific explanation that all actors in an event will leave evidence of their presence, not only on actors but scene; they also take away evidence of other actors on their person

Locard’s Triangle

3 major avenues available to police investigators for assistance in solving a crime

confession, eyewitnesses, evaluation of physical evidence from crime scene

why is physical evidence the most reliable

can’t be lied or coerced or misremembered (confession, eyewitness); is free from inherent error or bias

FBI

Federal Bureau of Investigation

DEA

Drug Enforcement Agency

ATF

The Bureau of Alcohol, Tobacco, Firearms, and Explosives

USPS

The United States Postal Service

IRS

Internal Revenue Service

DOD

Defensive Forensic Science Center

Sources of biological Evidence

blood, semen, saliva, and organs/ physiological fluids

Types of Physical Evidence

biological, handwriting analysis, drugs

types of drug evidence

alcohol, prescriptions, diverted pharmaceutics, explosives/petroleum products, materials (ie glass fiber, hair, etc), fingerprints, shoe prints, striations/toolmarks

diverted pharmaceutics

legal persecutions medications being sold or used by someone they were not initially intended for

striations (guns)

These are tiny, microscopic scratches inside the impression marks. They act like a fingerprint for the specific weapon

patterned evidence

fingerprints, firearms, treadwear, footwear, toolmarks, serial number restoration

Catch-up categories

plastic bags, powder residues, soil and minerals, vehicles lights

why examine physical evidence

comparison, individual characteristics (is there anything unique to single origin?) class characteristics (is there anything unique to certain group)

AFIS

automated fingerprint identification system

CODIS

combined DNA index system

NIBIN

National Integrated Ballistic Information Network

IBIS

Integrated Ballistic Identification System

PDQ

paint data query

SICAR

Shoeprint Image Capture and Retrieval

Blood Pattern Analysis

circumstances of crime, direction, velocity, size and mass,

Circumstances of crime (blood pattern analysis)

circumstances surrounding the crime including what happened, what weapon was used and who may have been involved

direction (blood pattern analysis)

can tell investigators how the victim and suspects were moving and their position in relation to one another

velocity (blood pattern analysis)

When a drop of blood exceeds a specific speed, the pressure from the air drag causes the drop to spatter into other smaller drops

size and mass (blood pattern analysis)

The size of the blood drop dictates the velocity in which it flew through the air. The mass of the blood drop is estimated by the width (diameter) of the drop and density (viscosity) of the blood.

arterial blood spray

bleed has a wavy, pulsing pattern because blood spurts out in synchronized waves with each heartbeat as the heart pumps high-pressure blood into the damaged artery

how arterial blood spurting works

Heart Action: The heart contracts (beats) and pushes blood out with high pressure

Pressure Peaks: Blood pressure rises when the heart beats and drops slightly when the heart rests between beats.

Wavy Pattern: This pulsing change in pressure creates a rising and falling flow, making the blood spurt out in waves instead of a steady stream.

Bright Color: Blood from an artery is rich in oxygen, so it looks bright red.

angles of impact (blood spatter)

the diameter of bloodstain increases as height increases

cast off stains

when a weapon is swung repeatedly blood might be thrown off it as it is reared back to strike again

cast off pattern at low velocity

cast off pattern at medium velocity

cast off patterns at high velocity

what is this pattern cause by?

hair swipe

what is this patten caused by?

hand swipe

what is this pattern caused by?

fabric swipe

back spatter

Biological material, such as blood or tissue, is ejected from a gunshot entrance wound back toward the direction of the shooter.

back spatter movement

It travels opposite to the line of fire, meaning it moves backward out of the hole the bullet just entered

back spatter causes

High-speed bullet impacts create pressure and physical forces (like Rayleigh-Taylor instability) that atomize and push fluids out of the entry wound.

back spatter droplet size

includes micro-stains (under 0.5 mm) as well as larger macro-stains.

back spatter distance

typically travels a short distance, often landing on the firearm, the shooter's hands, or nearby surfaces in close-range or contact shots

back spatter variables

The amount and pattern depend on the gun's caliber, distance, and the specific target area on the body. Muzzle gases from the gun can also interact with and influence the moving droplets.

what is this

a bullet wound, shows back and forward spatter from entry and exit wounds

what is a coroner

an elected official who may or may not have a medical degree

what is a medical examiner

an appointed official, usually a physician or board certified Forensic Pathologist responsible for certifying the manner and cause of death

who performs autopsies

pathologists

characteristics of a clinical autopsy

focus on internal

organs and medical condition

confirms clinical diagnosis

extent of diseased states

appropriateness of therapy

characteristics of forensics medicolegal autopsy

cause/manner of death

used in criminal proceedings

external and internal findings

establish correlations between injuries and crime scene

medicolegal death investigation

respond to the scene, document body and environmental findings, conduct witness interviews, and coordinate with law enforcement and medical staff.

forensic pathologist

These licensed physicians conduct post-mortem examinations and autopsies to identify internal trauma, disease processes, and precise causes of death

core investigation step of a medicolegal death investigation

scene assessment, autopsy and laboratory testing, manner determination

scene assessment (medicolegal death investigation)

Securing the location, noting body position, and collecting immediate physical evidence like medications or weapons

autopsy and laboratory testing (medicolegal death investigation)

Performing external and internal body assessments, microscopic tissue analysis, and toxicological screening for drugs or poisons.

manner determination (medicolegal death investigation)

Establishing whether the death was natural, accidental, suicide, or homicide based on synthesized multidisciplinary evidence.

cause of death

that which initiates the series of events ending in death (examples: Blunt force injury, Sharp force injury, Asphyxia, Gun shot wound, Substance abuse)

manner of death

circumstances that lead to the fatal result and is the culmination of complete death investigation, includes cause of death (examples: homicide, suicide, accidental, natural causes, undetermined)

manner vs cause of death

The cause of death is the specific disease or injury that starts the lethal chain of events, while the manner of death is the broad category explaining how those circumstances happened

strategies for estimating time of death

algor mortis, livor mortis, rigor mortis

algor mortis

equalization with the environmental temperature, lose heat at rate of 1-1.5 degrees an hour; is dependent on size of body, clothing, etc

livor mortis

ceasing of circulation; when heart stops pumping blood settles in part of body closer to the ground

rigor mortis

chemical changes that cause rigidity; condition evolves over 24-hour period and subsides typically within 36 hours

what happens seconds after death

ceasing of brain activity, body temperature drops

what happens minutes after death

beginning of putrefaction

putrefaction

cells die due to lack of oxygen and start to breakdown

what happens hours after death

calcium builds up cause’s rigor mortis, muscles eventually relax, skin shrinks making nails and hair appear to grow, livor mortis pulls blood to parts of body closes to ground

what happens days after death

parts turn green due to enzymes in organs digesting themselves, smell due to putrescine and cadaverine

what happens weeks after death

maggots/bugs digest body, turn purple to black as bacteria eats body, hair falls out

what happens months after death

about 4 months after soft tissues decompose until only skeleton

time frame of rigor mortis: 1-4 hours

jaws and neck rigid; rest of body limp

time frame of rigor mortis: up to 8 hours

everything down to legs is rigid

timeframe of rigor mortis: for 12 hours

everything in body remains rigid

time frame of rigor mortis: 24 hours

jaw is limp; rest of body rigid

timeframe of rigor mortis: 30-32 hours

everything but legs are limp

timeframe of rigor mortis: 36 hours

no rigidity

lividity

in livor mortis the bluish-purple discoloration of skin after death caused by pooling of blood in lowest part of body

blanching

in livor mortis where the skin is discolored white caused by the pooling of blood in body and pressure distribution

timeframe of livor mortis: 30mins to 4 hours

start of lividity

timeframe of livor mortis: 8-12 hours

blanching ends

timeframe of livor mortis: 12+ hours

blood becomes un-blanchable and fixed

what do lividity and blanching tell us?

time of death and position in which individual died, cause death based on lividity color

abrasions

when skin is rubbed off

lacerations

a cut that goes thru the layers of skin

contusion

a bruise

petechiae

hemorrhaging in the eyelids, indictive of strangulation

black eye (eyelid and under eye)

blunt force trauma directly to eye

black eye (eyelid)

indicates blunt forces trauma to the back of the head

stippling

burn marks from hot gun powder and soot from firearm discharge (shows fired at close range)

1st time fingerprints were used for identification

a prison in 1904

anthropometrics

a system of measurements taken to identify people; developed by Alphonse Bertillon; no longer used

volar pads

tissue that appears during gestation that helps produce fingerprints; develops across 6 to 17 weeks

1sts principle of fingerprints

an individual characteristic; no two fingers have yet been found to possess identical ridge characteristics

2nd principle of fingerprints

will remain unchanged during an individual’s lifetime-barring any severe disease or injury