Physical Evidence in the Courtroom



Physical Evidence in the Courtroom

Professor Anne Adams

Composed by Josh Dubs ’08

December 5, 2007

I. Autopsies

A. When done

1. Required by law under certain circumstances

a. Sudden death (including suicide)

i. Whenever there is no treating physician present to account for the cause

ii. Even when the cause is obvious

b. Where the cause of death is not apparent

c. Whenever the death was violent

i. Accidental or otherwise

d. Stillborn deaths or infant deaths (within 24 hours of birth)

e. Death while in police custody

f. When the body is unclaimed or unidentified

2. By request

a. Family, police, treating physician can request, but Medical Examiner has final decision

B. Procedure

1. Goals of autopsy

a. Identification of the victim

b. Cause of death

c. Manner of death

d. Health risks

i. To assure that the cause of death was not an epidemic of some sort

e. Preservation of evidence

i. In a murder, the body itself is a piece of evidence

ii. In a rape, the body is the primary crime scene

2. Procedure

a. Body is cut open

i. T-incision

ii. Y-incision

b. Organs removed and weighed

c. Body examined under black lights for bruises

d. Run toxicology test

C. Toxicology

1. Tested fluids

a. Blood from aorta

b. Bile from liver

c. Urine from bladder

d. Contents from stomach

e. Fluid from eyes

f. Tissue samples

2. Substances tested for

a. Illegal drugs

i. Amphetamines

ii. Opiates

iii. Cannibus

iv. Cocaine

v. PCP

vi. Does not test for date rape drugs unless asked

b. Pharmaceutical drugs

i. Sedatives

ii. Cardioactive agents (heart medication)

iii. Antipsychotic drugs

iv. Antiepileptic drugs

c. Non-medical toxins

i. Carbon monoxide

ii. Alcohol

iii. Cyanide

iv. Arsenic

v. Etc.

d. Levels

i. Therapeutic level

A. Prescription rate

ii. Toxic level

A. Poisonous in the body, but not necessarily the proximate cause of death

iii. Lethal level

A. Overdose

D. Time of death

1. Accuracy

a. Time of death is ALWAYS estimated

b. The sooner the Medical Examiner can examine a body, the tighter the estimate will be

2. Decomposition

a. Affected by conditions

i. Weather

A. Temperature

B. Wind

C. Humidity

D. Precipitation

ii. Environment

A. Exposure to animals, insects, etc.

B. Indoors vs. Outdoors

C. Land vs. Water

b. Affected by the body

i. Body mass

A. Skinnier people have less mass to decompose

ii. Bleeding

A. More bleeding = faster decomposition

iii. Clothing

A. Naked bodies decompose faster

E. Post-Mortem changes

1. Time of death

a. Skin becomes waxy and clammy

b. Face becomes pale

c. Corneas become milky and white

2. Rigor mortis

a. Occurs in a bell-curve

i. 2-4 hours after death, rigor mortis starts

ii. 12-24 hours after death, rigor mortis peaks

iii. Approximately 24 hours after death, rigor mortis begins to wane

iv. Approximately 36 hours after death, rigor mortis should have passed

b. Affecting rigor

i. Skinnier people develop rigor mortis faster than fat people

A. Some very fat people will not develop rigor mortis at all

ii. Heat will speed up rigor mortis

A. Cold will slow rigor mortis

iii. Adrenaline from cause of death can accelerate ricor mortis

3. Cadeveric spasm

a. Muscle lock

b. NOT related to rigor mortis

4. Lavidity

a. “Liver mortis”

b. Pooling and settling of blood within the blood vessels due to gravity

c. Begins approximately 30 minutes after death

i. The blood begins coagulating

d. Usually fixed within 4-5 hours

e. Will be totally set within 24 hours

f. Color of body differs by cause of death

i. Carbon Monoxide poisoning, body will look cherry colored

ii. Bleeding out, body will be white

iii. Asphyxiation, body will be deep red/purple

g. Can tell the position of the body immediately after death

i. But not necessarily at death

5. Stomach contents

a. Can be helpful in telling the cause of death, as long as there are contents

b. Will empty within 4-6 hours

i. Small intestines will empty within 12 hours

F. Dead Bodies

1. Effects of water

a. Body will sink in water and remain immersed

i. 8-10 hours in warm water

ii. Up to 3 weeks in cold water

b. Body will then rise to surface unless restricted

c. Other skin loosens in 5-6 days

d. Nails separate in 2-3 weeks

2. Insect activity

a. 10 minutes after death

i. Flies arrive and lay eggs in nose, mouth, and eyes

b. 12 hours

i. Eggs hatch and maggots feed on tissue

c. 24-36 hours

i. Beetles arrive and feast on dry skin

d. 48 hours

i. Spiders, mites and millipedes arrive to feed on the bugs which are there

II. Serology

A. Serology

1. The study of bodily fluids

2. Determinations

a. Is it blood?

b. Is it human?

c. Whose is it?

B. Serologists

1. Tests

a. Kassel-Meyer test

i. Basic blood test

b. Luminol and Flourezine

i. Used at crime scene on walls, bedsheets, stairs, and things that can’t be taken into the lab

2. Chemicals

a. Kassel-Meyer test

i. Phenal Thaline aused as a reagent

A. Is the sample turns bright pink, blood is present

b. Luminol

i. Chemoluminescence

A. Chemical reaction which causes lumination

B. Spray it, and it will glow on the surface

ii. Evidence-degradation

A. Studies have not shown that liminal affects DNA, but still must worry about degrading DNA

B. Chemical will destroy blood spatter if it is visible

iii. Timing

A. Will fade with time, so must take photographs

iv. Sensitivity

A. Super-sensitive

1. Will show the tiniest speck of blood on the whitest wall

c. Flourezine

i. Same as Luminol, but results are not visible except under blacklight or other alternate light source

C. Fluids

1. Semen

a. General

i. Standard ejaculate is 2-6 mL

ii. Approximately 100 million – 150 million sperm per ejaculate

b. Presumptive test

i. Looking for seminal acid phosphitates

ii. Brentamine Fast Blue test

A. Will find semen diluted up to 500x

B. Filter-paper method

1. If the paper turns purple then there is a presumptive-positive

c. Confirmatory test

i. Christmas-tree-stain test

A. Done after the Brentamine Fast Blue test

B. Dye is injected into the sample, which adheres only to the tips of the sperm, which indicate a positive test

d. Motile sperm

i. Sperm dies within 3-6 hours after leaving the man’s body

e. Semen density

i. Semen loses density with time

ii. Sperm will live if victim is living up to 7 days in vaginal cavity

iii. Sperm will live in rectal cavity for only 2-3 days

iv. Sperm will only live in mouth for approximately 24 hours

2. Saliva

a. Humans produce hundreds of liters of saliva per day

b. Looking for Amalayse

3. Fecal Matter

a. 1/3 of weight of fecal matter is pure bacteria

i. No DNA can survive

ii. Would NEVER test fecal matter for DNA

4. Urine

a. Can get some DNA from the epiphelial cells in the urinary tract

i. Very low concentration, however

5. Vomit

a. No real standard test for vomit

b. Will look for presence of amalayse and stomach contents

6. Vaginal secretions

a. Glyconated epiphelial cells

i. Produced by women of child-bearing age

A. Can sometimes be found in rape kit

ii. Found on foreign objects if inserted

A. Won’t always get a positive DNA test, but can show that the foreign object was inserted

D. Rape Kit

1. Generally

a. There is no medicinal purpose – strictly forensic and evidence-gathering!

b. There is a generic box containing instructions for the to use

i. Questionnaire to be filled out by nurse

ii. Everything is labeled with coded labels

iii. Swabs and paper containers

A. MUST HAVE PAPER CONTAINERS

c. Protocol

i. No standard protocol for conducting rape kits

A. Different jurisdictions, different hospitals have different protocol

ii. Some hospitals may refuse to do them for liability purposes

2. General Procedure

a. Oral swabs and smears taken

b. Nasal swab taken

c. Fingernail clippings (sometimes)

i. May take scrapings from underneath the fingernails

d. Known blood sample

i. Typically a pin prick from the victim

e. Head-hair sample

i. Must take 10-12 samples, and they must be plucked so as to include the root of the hair

f. Victim’s clothing collected on a clean sheet

i. Clothing to be dropped onto clean paper sheets on the floor and collected

g. Dried secretions on the victim’s body

i. Nurse must identify and hydrate, etc.

h. Pubic combing

i. Victim laid on a sterile paper sheet and pubic hair is combed to find foreign pubic hairs

ii. Must then get at least five known samples AFTER the combing

A. Again, hairs must be plucked to ensure that the hairs came from the victim

i. Genital swabbing

i. To look for evidence of saliva and semen

j. Anal swabbings and smears

k. Vaginal swabbing

l. Cervical swabbing

i. More important the longer it has been since the rape

m. Miscellaneous evidence

i. Tampons, bandages, etc.

n. Urine specimen

i. Looking for date-rape drugs, etc.

ii. May want a real blood sample (drawn rather than pricked) to compare

o. Nurse observations/questions

i. Alcohol on victim’s breath?

ii. Has there been any other sexual intercourse?

iii. Is the perp known to victim?

p. Notes

i. All swabs must be air-dried before being bagged

ii. Must use paper envelopes, NO PLASTIC

E. Chain of Custody

1. CRITICAL QUESTIONS

a. Has it been in the person’s dominion and control the entire time?

b. Has anyone done anything to alter or adulterate it?

2. General

a. Documenting who and in what order the samples have been tested

III. Fungible Evidence

A. Fungible evidence

1. Cash

2. Drugs

3. Blood

4. Etc.

B. Fibers

1. Analysis

a. Is it animal, vegetable, mineral, or synthetic?

i. Comparison

A. Color

B. Diameter of the fiber

C. Shape

D. Chemical composition

E. Molecular structure

1. Crystalline structure

ii. Class characteristics

A. Fibers belong to a group

1. Each group has individual characteristics

b. Animal

i. Fur

ii. Wool

iii. Hair

c. Vegetable

i. Cotton

ii. Flax

iii. Hemp

d. Mineral

i. Asbestos

ii. Fiberglass

e. Synthetics

i. Carpet

ii. Polyester

iii. Rayon

iv. Spandex

v. Acrylic

A. 24 categories of acrylic

vi. Nylon

C. Hair

1. Analysis

a. Measuring color, size, texture

2. Structure of a hair

a. Cortex

i. Like the wood of a pencil

b. Cuticle

i. Like the filling of a pencil

c. Medulla

i. Like the lead of a pencil

ii. Will be continuous, fragmented, interrupted, or outright absent

A. Human medullas are usually fragmented or interrupted

1. Except for Asians, usually continuous

iii. Degree of medullation

A. Ration between the medulla and the entire diameter of the hair

1. In humans, typically 1/3

2. In animals, typically 1/2

3. What you can tell from hair without DNA

a. Species

b. Race

i. Mongoloid, Caucasoid, Negroid

c. Location of growth

i. Uniform pigment and diameter in scalp hair

ii. Variation of diameter and continuous medulla in pubic hair

iii. Triangulation, blunt tips typically seen in beard hair

d. Presence of dyes or chemical treatments

i. Hair colors, etc.

e. Some diseases

i. Albinism

ii. Sickle-cell anemia, etc.

f. Drug use

4. What you cannot tell from hair without DNA

a. Sex

b. Age

i. Except infants, which have different hair

5. Collection

a. With tape or tweezers

b. Place in paper bags, NOT plastic

D. Glass

1. Trace evidence vs. fracture analysis

a. Glass is NOT a crystalline structure

i. Technically a liquid

b. Fractures concoidally

2. What to look for

a. Thickness

b. Color

c. Uniformity

d. Curvature

e. Surface

i. Irregularities like bubbles, etc.

3. Test

a. Refractive index

i. Measures velocity of light

A. Sparkliness

b. Color

i. Use a microspective photometer

c. Match point

i. The point at which the glass melts

4. What can be discovered

a. Type of trauma

i. Velocity of impact and type of impact

A. Blunt impact vs. sharp impact

b. Order of the impact

i. Radial cracks vs. concentric cracks

c. Concoidal lines

E. Microscopes

1. Basic compound microscope

a. Standard microscope

2. Comparison microscope

a. Gives two comparing images

b. Used to compare ballistics

3. Stereoscopic microscope

a. Gives 3-D image

b. Can magnify 10-125x

4. Microspective photometer

a. Measures light absorbtion

i. Gives an exact measure of color (dark blue vs. very dark blue, etc

5. Scanning Electron Microscope

a. Magnifies 10-100,000x

b. Used to see gunshot residue

IV. Weaponry

A. Types of guns

1. Handgun

a. Single-shot pistol

b. Derringer

i. Two-shot pistol

c. Revolver

i. Most common weapon in the U.S.

ii. Types

A. Swing-out

1. Cylinder swings out to the side

B. Break top

1. Barrel cracks in the middle, which reveals the cylinder

C. Solid Frame

iii. Actions

A. Single-action

1. Must cock the hammer first, then press the trigger to gire

2. Requires less pressure to depress the trigger

B. Double-action

1. Only press the trigger, hammer will cock itself then fire

2. Requires more pressure to depress the trigger

C. Semi/Automatic

1. Auto-loading

2. Force from the discharge forces the next bullet into the chamber

D. Automatic

1. More than one round comes out when the trigger is depressed

E. Semi-Automatic

1. Only one round comes out when the trigger is depress

2. Shotgun

a. Single-shot shotgun

b. Double-shot shotgun

c. Lever/bolt/pump action

d. Minimal barrel length is 18”

e. Smooth-bore

3. Rifle

a. Single-shot rifle

b. Lever/bolt/pump action

c. Automatic

d. Minimal barrel length is 16”

e. Has lands and grooves inside the barrel

4. Sub-machine gun

5. Machine gun

B. Calibers

1. In principle

a. The diameter of the bore from land to land

2. In reality

a. Rarely accurate

i. .357 magnum vs. .38 special

A. Not very much difference between them

V. Gunshot Wounds

A. Types

1. Perforating

a. Goes in, comes out

2. Penetrating

a. Goes in, but doesn’t come out

B. Categories

1. Contact wound

a. Hard contact

i. Some pressure on the skin by the weapon

ii. Soot pattern will be tight, dense and regular

iii. Skin is burnt

A. Powder will not wipe off, but is actually burnt onto the skin

b. Loose contact

i. Little or no pressure, but weapon still in contact with the skin

ii. Some blowback against the skin

c. Angled contact

i. Weapon tipped up

ii. Soot pattern will be oblong

d. Incomplete contact

i. Weapon against a circular or cylindrical surgace

ii. Tighter, denser, pear-shaped pattern

2. Near-contact wound

a. Very similar to loose contact wound

b. Weapon not in contact with skin, but close

c. Soot pattern is wider

d. Near-Contact angled wound

i. Very very similar to angled contact wound

ii. Soot pattern much broader

A. Soot also will blow behind the bullet

iii. Medical examiner must trace the path of the bullet to determine whether or not the wound was a contact or near-contact wound

3. Intermediate wound

a. Begins at about 10 mm between the weapon and victim

b. Powder tattooing

i. Typical in intermediate wounds

ii. Punctate abrasions

A. Not the result of a burn!

iii. Can be wiped away

iv. Not seen on hands or feet

A. Skin is too tough for punctate abrasions

v. Differences

A. Antemortum – reddish-brown, orange-red

B. Postmortum – grey, yellow, ashy

4. Distant wound

a. Entrance wound

i. Abrasion ring

A. Will not have one if there is a super-high velocity bullet

B. Won’t have one on the hands or feet

1. Skin too tough

5. Suppressors

a. Silencer

b. Flash suppressor

i. Diffuses the flame that shoots out of a rifle barrel

A. Increases difficulty in seeing where the bullet came from

C. Exit Wounds

1. Stellite

a. Tight skin

2. Slit

a. Lax skin

3. Crescent

a. Most common

4. Shored

a. When the bullet ricochets off surface behind them and reenters the body

i. From victim being against a cement wall, or from wearing tight pants or pantyhose, etc.

5. Bone chips

a. Always go the direction of the bullet

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