TSA - Forensic Science

Death

the cessation, or end, of life

-Cessation of all brain activity

-Irreversible cessation of blood circulation

-Experts do not agree on a single definition

Why is it impossible to determine the exact moment of death?

Many different people have different versions of what death is. Some people say that a person has died when there is no brain activity, and others say that the moment of death occurs when blood circulation stops with the body.

Cause of Death (COD)

Event that directly caused death (reason for death)

Mechanism of death

the specific change in the body that brought about the cessation of life

Types of Death

Natural, accidental, suicide, homicide, or undetermined

-Traumatic: suicide, homicide, and accidental

Considered Trauma

Thermal - Burn-related injury (including fire, chemical, radiation, or electrical contact)

Mechanical - Blow, crushed, cut or penetrating wound

Chemical - Corrosive substance affects skin, eyes, mouth, or internal organs

Exsanguination

bleeding to death

Blunt force trauma

injury caused by a blow that does not penetrate the skin or other body tissues

Asphyxiation

a medical term for suffocation, which leads to lack of oxygen in the blood.

Dyadic Death

Homicide followed by the suicide of the perpetrator

Equivocal Death

manner of death (homicide, suicide, accident) remains undetermined after a complete investigation.

Dactyloscopy

the study of fingerprints

3 Basic Fingerprints

-Whorl: Form circular or spiral patterns. 25% of the population has it.

-Arched: Ridged that form a wave-like pattern. 5% of the population has it.

-Loop: One or more ridges enter on either side of the impression. 70% of the population has it.

What is the average number of ridges on a human adults finger each?

150 Ridges

What is the cause of finger ridge patterns?

The amount and location of vollmer pads in thick skin

Latent Fingerprints

A hidden fingerprint made visible through the use of powders or other techniques. Not visible to the naked eyes. 85-90% leave latent prints (invisible)

Patent Fingerprints

A visible fingerprint that happens when fingers with blood, ink, or some other substance on them touch a surface and transfer the pattern of their fingerprint to that surface.

Plastic Fingerprints

3D Impression into an object (wax, butter, etc.)

Source of Residue (Fingerprints)

Oil on fingers keeps them lubricated and protected. 1-2% of secretion is amino acids, salts, etc.

When are fingerprints developed in the womb?

Develop in the womb fully by 6 months, beginning during the 17th week/3rd month of pregnancy

Secretor vs. Non-secretor

Secretor = People who leave fingerprints

Non-Secretor = People who don't leave fingerprints

AFIS (Automated Fingerprint Identification System)

A computer database of scanned and encoded fingerprints. A.F.I.S. can quickly search known files for comparison and matching to unknown fingerprints. A.F.I.S. is maintained by the F.B.I.

Blood stain pattern analysis

the interpretation of bloodstains at a crime scene in order to recreate the actions that caused the bloodshed.

Back Spatter

blood directed back toward the source of energy or force that caused the spatter; often associated with entrance gunshot wounds

Blunt Force Trauma (Blood Stains)

Larger surface area will collect more blood, producing drops of various sizes.

Sharp force injuries

Less blood being deposited on the instrument, smaller more linear patterns of stains; often associated with stabbing.

Impact (Blood Stains)

Blood projecting throughout air and seen as splatters.

Passive (Blood Stains)

Drops, flows, and pools due to gravity.

Transfer (Blood Stains)

Object comes into contact with existing blood stains and leaving wipes, smears, or pattern stains.

Gunshot Splatter

Forward splatter from exit wound and back splatter from entrance wound.

Expired Splatter

Blood from an internal injury mixing with air from lungs being expelled through the nose, mouth, or an injury to airways or lungs, forms a very fine mist and some blood stains are latent.

Arterial Spray

Spurt of blood when a major artery is severed with new pattern created each time the heart pumps.

Cast-Off

Object swung in an arc flings blood onto nearby surfaces. Assailant swings bloodstained object back before inflicting another blow.

Void Pattern

is created when n item is removed from the area after bloodstain spatter has been created.

Projection Splatter

Caused by arterial spurting, expirated spray or splatter cast off an object.

High-Velocity Impact Splatter

A bloodstain pattern caused by a high speed impact or force to a blood source such as that produced by gunshot, velocity may be 100 ft/sec, generally forming drops less than 1 mm.

Contact (Blood Stains)

Blood deposited from direct contact between 2 surfaces; at least one is bloody.

Flow (Blood Stains)

Change in shape and direction of blood stain due to gravity or movement of object.

Evidence

the available body of facts or information indicating whether a belief or proposition is true or valid.

Forms of evidence

physical, documentary, demonstrative, judicial notice, testimonial

Types of Evidence

Testimonial, Physical, Trace (when objects make contact)

Order of collecting evidence at a scence

1) Photograph and document scene

2) Collect trace materials (especially from points of entry)

3) Collect DNA by swabbing areas of contact

4) Collect other biological evidence

5) Locate and collect latent fingerprints

What will evidence collected do for the investigation?

-May prove that a crime has been committed

-Establish any key elements of a crime

-Link a suspect with a crime scene or victim

-Establish identity of a victim or suspect

-Corroborate verbal witness testimony

Evidence is considered valuable if---

It is unique, has a low probability of occurring by chance, is in consistent with setting or character, and/or has a physical match via trace evidence.

Evidence Inventory

the physical accounting of evidence and records related thereto.

Evidence Submission Form

form used to receive evidence into the laboratory and to initiate request for laboratory examinations or analyses.

Evidence Vault(s)

a secured room or rooms for the storage of custody items.

Evidence Technician

person who is responsible for identifying, documenting, collecting and preserving items of evidentiary.

Evidence Collection Unit

Preservation of physical evidence

Evidence Transfer

A change in the possession of a custody item that must be documented in two specified locations (submitter and receiver). Transfers can occur from person to person, person to secure place, or secure place to secure place.

Evidence Indentifiers

Tape, labels, containers, and string tags used to identify the evidence, the person collecting the evidence, date evidence was gathered, basic criminal offense information, and a brief description of pertinent evidence.

Section Evidence Area

A secured room or cabinet for temporary storage of evidence by analysts.

Associative Evidence

Evidence that may link suspect to the crime; answers "who did this?"

Examples: Fingerprints, bodily fluids, blood, weapons, hair, fiber, etc.

Circumstantial Evidence

evidence based on suggestion rather than personal knowledge or observation.

Class Evidence

Specific enough to identify overall characteristics but not unique identification to the source.

Corroborating Evidence

Tends to support a proposition that is already supporting by some evidence.

Direct Evidence

evidence that (if true) proves an alleged fact, such as an eyewitness account of a crime.

Exculpatory Evidence

Evidence that suggests the defendant's innocence.

Forensic Evidence

Evidence obtained through scientific techniques of analyzing physical evidence.

Hearsay Evidence

Evidence given by a witness based on information received from someone else rather than personal knowledge; In some courts, it is unadmissable.

Inconsistent Evidence

Something that is not uniform or not the same throughout.

Inculpatory Evidence

Shows people's involvement in an act -- used to criminate defendant.

Indirect Evidence

Another word for circumstantial evidence

Individual Characteristic Evidence

Associates particular individual with the commission of a crime

Reconstructive Evidence

Any form of evidence that helps determine what actually happened at the crime scene and the sequence of events; answers "How did it happen?"

Examples: Broken window, blood splatter, shoe prints, etc.

Transient Evidence

Is temporary; easily changed or lost; usually observed by the first officer at the scene.

Examples: Odors, temperature, footprints

Unique Evidence

Being one of a kind, particular to a certain clue.

Statistical Evidence

Data collected by polling and research studies that can be used to make statistical generalizations.

Prime Facie Evidence

"On it's 1st appearance." Presented before a trial that is enough to prove something until it is successfully disproved or rebutted at trial.

Also called "Presumptive Evidence."

Documentary Evidence

Written contracts, sales slips, letters, or affidavits (sworn statements)

Digital Evidence

Evidence consisting of information stored or transmitted in electronic form.

Impression Evidence

Objects or materials that have retained the characteristics of other objects through direct contact.

Examples: Shoe prints, bite marks, etc.

Forensic Entomology

Study of insects in corpses

-Collects insects from on, above, and below the body

-Records environmental conditions

-Provides data used to estimate the time that elapsed between the actual death and when then body was first discovered

Subdivisions of Entomology

-Urban: Involves civil and legal crimes

-Stored Product Pests: Involves food contamination

-Medicolegal: Centered on criminal component of human remains

By inspecting the corpse, insect life cycle provides a benchmark of time of death. Cannot provide an exact time of death due to fluctuating environmental conditions.

Within minutes, certain insects arrive to lay their eggs on the warm body - blowflies - attracted to smell of 1st stage of decomposition (takes place at surprisingly consistent time intervals)

Life Cycle of Flies

1) Eggs: Hatch within 24 hours of being laid

2) 1st Instar: Stage of maggot larvae

-Crawl to the closest food source and begin to eat

-Will double in size over the next 27 hours

3) 2nd Instar:

-Maggots shed their old skin

-Continue to eat and grow until shedding after 22 more hours

4) 3rd Instar: 2nd parts that last 100 hours in total

-Feeding: Continue to grow and eat

-Migrating: Continue to eat and grow until shedding after 22 more hours

5) Pupae: enclose themselves in a hard shell and begin metamorphosis

6) Adult: Convert into an adult eventually

Stage of Decomposition (Entomology)

-Carrion flies attracted to: Bloated Corpse

-Blow flies attracted to: Fresh Corpse

Carrion

insects associated with decomposing remains

1) Blow Flies (Calliphoridae)

-Iridescent flies with blue, green, copper, or black bodies

2) Fresh Flies (Sarcophagidae)

-Grayish, usually with 3 distinct longitudinal dark stripes on the dorsal thorax

Oviposition

The egg laying process

Factors affecting insect development

Temperature, moisture, wind, time of day, season, exposure to the elements and variations among individual insects

Insect Arrival Sequence

Blowflies→ tiny wasps (attracted to seeping fluid) → mites and beetles (favor drier conditions)

How Different Seasons Affect PMI of Body

-Some fly species are active in the early spring, different species are active in the fall, and others are continuously active

-If an insect larvae is more abundant in the fall is discovered, this can indicate the body was undiscovered for many months, while if larvae are found from spring flies. This could indicate the cadaver is more recent, or that it was recently exposed to the newly emerged adult flies.

Forensic Toxicology

the science of detecting and identifying drugs and poisons a person may have used for medicinal, recreational, or criminal purposes

People can be exposed to toxic substances:

Intentionally - By treating illness or relieving pain

Accidentally - By harmful combinations or overdoses

Deliberately - By harming or killing others, or by suicide

What is the percentage of homicides caused by poisoning?

.005%

What is the difference between poison and toxins?

Poison = Chemicals that can harm the body if ingested, absorbed, or inhaled in sufficiently high concentrations.

Toxins = Poison produced naturally by organisms

Methods of poisoning

Ingesting, inhaling, injecting, absorbing

Determining alcohol levels

Urine, blood, field sobriety, breathe tests

Chemical and Toxic Substance List

A list of recognized chemicals and toxic substances in the laboratory facilities

Drug Control Laws

Established the severity of the a penalty associated with the manufacture, distribution, possession, and use of a drug may depend on the weight of the drug or its concentration in a mixture

Drug Standards Inventory

The physical accounting of drug standards used in the Chemistry and Toxicology Sections.

Drug Chemistry Section

The discipline responsible for the analyzes of any substance seized under the state's laws restricting the sale, manufacture, distribution and use of abusive-type drugs.

5 Types of Toxic Substances

1) Halluciongens (Psychedelics)

2) Stimulants

3) Depressants

4) Opiates (Narcotics)

5) Anabolic Steroids

What are the stages of death?

1) Pallor Mortis

2) Algor Mortis

3) Rigor Mortis

4) Livor Mortis

Pallor Mortis

"Paleness of death"; The gradual paleness of the skin that develops immediately after death as circulation stops (mostly seen in fair-skinned people)

Collapse of capillary circulation

Algor Mortis

The cooling of the body after death. Decreases in temperature 1.5 degrees per hour from normal body temperature (37 c (98 f)).

Can estimate time between death and when the body had been discovered. As decomposition occurs, internal body temperature rises.

Rigor Mortis

Stiffness of death

Livor Mortis

The pooling of the blood in tissues after death resulting in a reddish color to the skin. Discoloration of skin.

After 2 hours - Dark purple or blue splotches form

After 5-6 hours - Blotches become white

Can estimate time and/or cause of death based on lividity (discoloration, last 36 hours) and coloration.

Post Mortem Interval (PMI)

The time that has elapsed since a person has died.

-Recent PMI (0-50 hours) is estimated by a medical examiner based on physical changes to the body

-If a body remains exposed to the environment for a longer period of time, the normal physical changes observed after death may not provide an accurate PMI estimate

-Less than 3: Body is warm and stiffness in far extremities and small muscles only

-3-8 Hours: Body is warm and stiffness present in middle extremities and middle muscles only

-8-36 hours: Body is cold and stiffness is present throughout the day

-Over 36 hours: Body is cold and no stiffness

Stages of Decomposition

Fresh, Bloated, Active Decay, Dry Decay

*Flesh rots quicker next to fire