forensic test 2

death

cessation of life, all brain activity, the circulation of blood

coroner

elected or appointed; id the body, notify the family, collect and reuse personal items, issue a death certificate

medical examiner

must be medical doctor; performs autopsies to establish cause, manner, and mechanism of death

forensic pathologist

must be medical doctor; performs autopsies in the case of sus deaths; determines presence of disease, injury, poison. has training in toxicology, firearms, ballistic wounds, pathology

crowners

britian tax collectors, certified manner of death became known as coroners

cause of death

reason someone dies

mechanism of death

The specific change in the body that brought about the cessation of life; Loss of blood after a shooting; Cardiac arrest after a heart attack

process of death

stoppage; heart stops and cells begin to die

manner of death

Natural death; Accidental death; Suicide; Homicide; Undetermined

autolysis

cellular demolition; cell membrane ruptures

natural death

The interruption and failure of bodily functions

accidental death

death caused by unplanned events

suicide

person purposely kills themselves

homicide

Death of a person caused by another person

undetermined death

cause unknown

algor motis

Cooling of the body following death

Body temp. Moves toward the ambient (surrounding) temperature

livor mortis

The setting of blood cells due to the force of gravity

AS blood vessels break down, the reddish material pools at the lowest areas of the body

lividity

The reddish-purple color that happens in livor mortis

blanching

areas of pressure (shoulders, elbows, hip bones) blood cant reach area and will lack coloration

lividity found in two places

the dual livity is evidence that the body was kept in one position for at least two hours and moved to a second position before livity become permanent

rigor mortis

death stiffness; calcium accumulates in the muscle tissue and the muscles remain rigid until autolysis occurs

Stiffness progresses from the smaller muscle groups to the larger muscle groups

2-6 hrs: rigor begins

12 hrs: rigor completes

36+ hrs: rigor absent

postmortem changes in the eye

Surface of eye dries out following death

Develops cloudy film

2-3 hours if eyes are open at death

Tache noir (dark and cloudy discoloration)

decomposition

Primary source of bacteria in the body is the gastrointestinal tract

fresh stage of decomposition

first stage; Bacteria in the digestive tract begins to digest intestines, blue/green discoloration in the lower right area of the abdomen

bloated stage of decomposition

Bacteria causes gas to build up and tissues begins to swell

Strong smells attract flies

Blood vessels become discolored (marbling)

decay stage of decomposition

Tissues begin to turn blackish/blue

Fluids forced through openings in the body

dry stage of decomposition

Collapse of the chest and abdomen area are soft tissues have decomposed

Skelotonization stage of decomposition

Little to no soft tissue

factors affecting heat loss

body surface area, body position, physical activity, clothing, colder environment, wind, submerged bodies

probable causes of death

The event or reason that led to a person's death, Blunt force trauma, Sharp force trauma, Asphyxiation, Gunshot, Fire, Drowning, Substance related

blunt force trauma

Caused by objects with relatively broad and/or rounded edges

abrasions

Scraping and removal of the surface layer of skin; scratches and grazes

contusions

skin not broken; bruises, black and blue marks

lacerations

Tears in tissue; external (skin) or internal (organs)

Jagged edges

trace evidence can occur

sharp force trauma

A wound or injury caused by a sharp object

incised wounds

cuts; sharp object drawn across skin; longer than deeper

Defensive Wounds: sustained by those defending themselves

Hesitation Wounds: seen in suicides and attempted suicides as victims gather courage

stab wounds

Sharp object driven into body

Deeper than longer

Seen in homicides and suicides

Multiple stab wounds may indicate emotional stress

Exact length of object can not be determined as area of wound may have been compressed

langer lines

elastic fibers in the skin

langer lines

cleavage lines or tension lines, are lines that indicate the orientation of collagen fibers and muscle fibers in the human body

asphyxia

Body can’t take in any O2 or eliminate any CO2

Unconsciousness leading to death

suffocation

Air can't reach the lungs

smothering suffocation

nose and mouth are blocked, no external signs but material may be present around nose and mouth

choking suffocation

Obstruction of the air passage

mechanical suffocation

Pressure on the outside of the body prevents breathing

Usually accidental

strangulation

Construction/compression of the neck

Obstructs blood vessels and air passages

hanging

Mostly suicidal

Partial or full suspension

Weight of the body tightens the rope, cord, etc.

ligature stangulation

Band tightened by force causing pressure on neck

Homicide (rope, electric cord, nylon stockings)

Ligature mark is usually horizontal

manual strangulation

pressure on the neck from hand, arm, or limb; small red to purple spots

chemical asphyxia

Inhales gas that prevents body from using O2

CO2, cyanide

When you breathe in carbon monoxide, the poison replaces the oxygen in your bloodstream. Your heart, brain, and body then become starved of oxygen

electrocution

rare, accidental; Electricity runs from point of contact, through the body, to the grounding point

fire

Most fires are accidental but can be set to destroy evidence of the crime

Most lose consciousness and die from smoke inhalation rather than burns

autopsy

A medical exam performed by a medical examiner or pathologist to determine the cause and manner and mechanisms of death

clinical autopsy

done for medical research study purposes when foul play is not considered

forensic autopsy

provide expert witness testimony on both medical and legal issues

external autopsy

The body is photographed and X- rayed

Body bag examined for insect and trace evidence

Clothes are closely examined for trace evidence

Hands are examined if bagged

Fingerprints taken

internal autopsy

Y- shaped incision is made

Internal organs removed

Stomach contents examined

Brain is removed

Body is sewn up and prepared for the funeral home

non-biological indicators PMI

Cell phone use

Credit card use

Watch broken at scene

Interviews with family and friends to determine when the individual was last seen

biological time indicators PMI

Stomach and intestinal contents

2-6 hours- undigested stomach contents are present

6 -12 hours- stomach is empty but food is found in the small intestine

12 hours plus - small intestine empty waste found in the large intestine.

Changes in eye color cloudy film develops within 2 hrs

Degree of algore, rigor, and livor mortis

Insect activity

blood stain

a deposit of blood on a surface

blood splatter

a bloodstain resulting from blood dispersed through the air due to an external force other than gravity

are the stain patterns consistent with

statements given by witnesses, statements from victim or suspect, actions of both

history of forensic blood analysis

Herbert MacDonnell publishes Flight Characteristics and Stain Patterns of Human Blood, OJ simpson trial, SWGS

red blood cells

carries mainly oxygen and carbon dioxide to all parts of the body

white blood cells

fight disease and foreign elements

platelets

aid in blood clotting and repairing damaged blood vessels

cohesion

The blood mixture is attracted to similar blood mixtures and tends to stick together as it falls and not separate

This results in a perfectly spherical shape unless other forces act upon it

adhesion

Is the attraction between molecules of unlike substances

When blood comes into contact with another surface the blood tends to adhere to that surface

The smoother (nonporous) the surface, the rounder and more circular the pattern

The rougher (porous) the surface, the edges of the drop will break apart forming satellites or extensions

arterial spurt

Each time the heart beats, blood is forced out under pressure

gravity

The farther the blood drop falls, the larger the diameter of the stain

forces affecting blood splatter

cohesion, adhesion, arterial spurt, gravity. Due to these forces, the blood drop will remain circular or roundish and not break apart unless acted on by an outside force, or when it hits a surface

directionality

Blood tends to stick to the surface it touches

Momentum keeps the blood moving in the direction it was traveling

The pointed or elongated end (tail) points in the direction the blood is traveling

passive stains

drops, flows, pools

drops

A bloodstain pattern which results from blood dripping

A result from gravity

flow

The direction of a bloodstain due to the influence of gravity

A change in the shape or direction of a bloodstain may be due to the movement of the object

pooling

Bloodstain resulting from the accumulation of blood on a surface

contact stains

wipes, swipes, transfer pattern

wipes

A bloodstain pattern created when an object moves through an existing stain, removing and/or altering its appearance

swipe

The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered surface

transfer pattern

A bloodstain pattern created when a wet, bloody surface comes in contact with a second surface. A recognizable image may be observed in the pattern.

impact stain

spatter, cast off, arterial

splatter

A bloodstain which results from a blood drop being dispersed through the air due to an external force

cast off

A bloodstain pattern resulting from blood drops released from an object due to its motion.

arterial spurt pattern

A bloodstain pattern resulting from the ejection of a volume of blood under pressure

lines of convergence

Lines are drawn through the long axes of the spatter and opposite the direction of travel

Note where the lines intersect

angle of impact

The angle formed when blood strikes a surface

As the angle of impact decreases from 90º to 10º bloodstained shape become less round and more elliptical

When the width is divided by the length, the result is the sine of the impact angle

Calculating the angle of impact involves the measurement of the length and width of the stain

point of origin

The area in space where the blood spatter/injury originated

This three-dimensional area should be the size of a grapefruit.

Determine angle of impact of each stain

Using a protractor or laser: calculate the angle, attach string and secure.

investigating blood evidence at crime scene

Walk through and information gathering

• Care must be taken to avoid disturbing any blood evidence

• CSIs need to gather information prior to collecting evidence

Documentation of evidence

• Spray the area with chemical reagents

• Confirmation of human blood

Collection of blood evidence

• Packaged separately and labeled

• collected in clean, unused plastic sealed containers

• Dried blood packaged in a paper bag

• Wet bloodstains

bloodstain analysts

Can be law enforcement or lab staff

Formal training in blood pattern analysis (Competency testing, Continuing education)

Many have college degrees

forensic dna analysis

It has the potential to individually identify a particular suspect

Forensic DNA analysis identifies individuals, closely related relatives, remains of mass disaster war victims, and missing persons.

dna profiling

Techniques that identifies a person based on their genetic code; No two people share the same DNA, Exception is identical twins, DNA is inherited from the mother and father, Can be used to determine kinship (closely related individuals)

CODIS

a database of arrestee’s DNA, collects, analyzes, and communicated criminal DNA information among law enforcement agencies, maintains DNA profiles of missing persons and unidentified human remains period

limiting factors

cost, time log, backlogs, instrumentation

DNA identification act

provides funds to improve labs and communication between law enforcement organizations period; new rapid dna testing kits (90 min)

science of dna

all human cells contain dna (except red blood cells), contains dna in cells nucleus (nuclear dna), structure of dna is a double helix which resembles a twisted ladder

chromosomes

Structure where nuclear DNA is stored.

46 chromosomes are found in the human body. They are composed of tightly coiled DNA molecules wrapped around proteins.

Each parent contributes 1 member of each pair of the 22 chromosomes plus one sex chromosome (male XX, female XY)

Your genetic code is composed of half of your mother's chromosomes and half of your father's chromosomes.

genes

basic units of heredity; human gene DNA sequences are 99.% the same, the 0.1% is what makes us different; alternative forms of a gene are alleles

precautions to avoid contamination

Use disposable instruments

Wear disposable gloves and change them often

Avoid touching areas where DNA may exist

Avoid touching your face

Never put two sources of DNA in the same bag

preservation of dna evidence

Keep DNA evidence dry, cool, and out of direct sunlight during transportation and storage

Moisture

Humidity

serologist

One who specializes in the analysis of blood serum, saliva, semen, and other bodily fluids; determine if source is human

mtDNA

is responsible for cellular respiration and energy.

Only the mother can pass mtDNA to her offspring and thus maternal ancestry can be traced using this type of DNA.

Unlike the limited amount of DNA found in nuclear DNA, the mitochondria can supply thousands of copies.