Forensics - Week 7 - Entomology, Anthropology and Taphonomy

Forensic Entomology

The study of insects and arthropods associated with legal investigations.

Primary goal of forensic entomology

Estimate the post-mortem interval (PMI).

Sund Tz'u

Chinese death investigator (1235 AD) who wrote 'The Washing Away of Wrongs'.

'The Washing Away of Wrongs'

Earliest known text describing forensic entomology.

Board Certified Forensic Entomologist

Scientist certified to practice medico-legal entomology after exams and peer review.

How often must forensic entomologists re-certify?

Every 5 years.

Blowflies

Most common insects used to estimate PMI and usually the first to colonize a body.

Blowfly life cycle

Egg → Larva → Pupa → Adult.

Instars

The three developmental stages of larval maggots.

Larvae (maggots)

Fly larvae that feed on decomposing tissue.

Calliphoridae

Family containing bluebottle and greenbottle flies.

Phoridae

Coffin flies that can colonize buried remains.

Piophilidae

Cheese skipper flies often present later in decomposition.

Sarcophagidae

Flesh flies that deposit larvae instead of eggs.

Coleoptera

Order of insects that includes beetles.

Role of beetles in decomposition

Feed on larvae and dry tissues.

Examples of forensic beetles

Clown beetles, rove beetles, carrion beetles, ground beetles.

Decomposition

The breakdown of biological material after death.

Fresh stage

Early stage after death with little odor and minimal insect activity.

Bloated stage

Gas buildup from bacteria causes body swelling and strong odor.

Active decay stage

Large tissue loss, strong odor, heavy insect activity.

Advanced decay stage

Most soft tissue removed but some moist tissue remains.

Dry/remains stage

Mostly bones, cartilage, and dry skin remain.

Factors defining decomposition stages

Physical characteristics, insect populations, and VOCs.

Most important environmental factor affecting decomposition

Temperature.

Post-Mortem Interval (PMI)

The total time since death.

Minimum Post-Mortem Interval (minPMI)

Time since the first insects laid eggs on the body.

Time of Colonization (TOC)

Estimated time insects first colonized the body.

Pre-colonization interval

Time between death and insect arrival.

Post-colonization interval

Time after insects colonize the body.

Myiasis

Insect infestation of living tissue.

Method 1 for determining PMI

Insect development.

Method 2 for determining PMI

Insect succession.

Insect development method

Aging the oldest immature insects to estimate PMI.

Time scale for insect development method

Hours to weeks.

Insect succession method

Uses predictable order of insect species arriving on a body.

Time scale for insect succession method

Weeks to years.

Why temperature is important

Insects develop faster in warmer temperatures.

ADD

Accumulated Degree Days used to estimate insect growth.

ADH

Accumulated Degree Hours used to estimate insect growth.

Entomotoxicology

Study of drugs and toxins found in insects feeding on a body.

Bioaccumulation

Build-up of toxins or drugs inside insect tissues.

Other uses of forensic entomology

Detect neglect, body movement, body disposal, and DNA evidence.

Forensic Taphonomy

The study of post-mortem processes affecting decomposition and preservation.

Meaning of 'taphos'

Burial.

Meaning of 'nomos'

Law or study.

Taphonomic factors

Environmental factors that influence decomposition.

Examples of taphonomic factors

Temperature, soil type, burial depth, animals, plants, season.

Forensic Anthropology

Application of anthropology to legal investigations involving human remains.

Meaning of 'anthropos'

Human.

Goals of forensic anthropology

Identify victim, estimate PMI, determine cause and manner of death.

Bone characteristics

Bone is living, dynamic, and adaptive tissue.

Functions of bone

Support, protection, mobility, and mineral storage.

Cortical bone

Strong outer layer of bone.

Spongy bone

Porous inner bone structure.

Medullary cavity

Hollow center of long bones.

Types of bones

Long, short, flat, irregular, and sesamoid bones.

How many bones do newborns have?

About 300 bones.

How many bones do adults have?

206 bones.

Information bones can reveal

Sex, age, ancestry, stature, trauma, and disease.

Pelvis sex differences

Females have wider subpubic angle, wider sciatic notch, and larger pelvic inlet.

Cranium sex differences

Males have larger ridges, square chin, larger mastoid process, and sloped forehead.

Age estimation from bones

Based on teeth, bone fusion, and bone density.

Stature estimation

Long bone length correlates with height.

Osteometric board

Tool used to measure long bones for stature estimation.

Antemortem trauma

Injury occurring before death showing healing.

Perimortem trauma

Injury occurring at or around the time of death.

Postmortem trauma

Damage occurring after death.

Individualization

Unique skeletal features that help identify a person.

Facial reconstruction

Process of recreating a person's face from the skull.

Limitation of facial reconstruction

Not considered positive identification.

Methods to date skeletal remains

Carbon dating, amino acid analysis, nitrogen levels, immunology tests.

Roles of forensic anthropologists

Consultants, researchers, expert witnesses, and disaster investigators.