Crime Scene Investigation and Death Investigation

Preliminary Actions by the First Responder

-deal with emergencies

-identify, separate, detain and obtain any immediately helpful info from the crime report(s)

-summon assistance

-secure the scene

-avoid disturbing the scene as much as possible

-keep a security log

7S’s of Crime Scene Investigation

-secure the scene

-separate witnesses

-scan the scene

-see the scene (photos)

-sketch the scene

-search for evidence

-secure and collect evidence

Scan the scene

-stop

-walk through (not always possible)

-recognize: what is pertinent, what is extraneous, when in doubt collect it

-is this a primary or secondary scene

Sketching the scene

-label north

-add a scale of distance and legend

-all major objects included

-all evidence should be measured from two immovable landmarks

-include date, time, location, case #, crime type, names

-at the scene create a preliminary sketch

See the scene (photography)

-video used in conjunction

-capture: overall, intermediate, close up and examination images with accurate spatial relationships

-avoid color and lighting distortion

-take photos with and without markers and rulers

Types of search

-lane/strip search

-grid search

-zone search

-spiral search

lane/strip search

-walk in a line side by side, view your lane

grid search

-used to look for smaller details

zone search

-section off into square areas, search each zone

spiral search

-start in the center and make your way outward

-used when may not know how big a scene is

Collection prioritization

-immediate: possible DNA

-High priority: DNA, high relevance to case, making scene safe, disturbability

-low priority: stuff that won’t decay or disrupt the scene

Wet evidence

-temporary wet storage

-dry

-when dry store in breathable container

-dry evidence to prevent mold

Chain of custody

-a process used to maintain and document the chronological history of the evidence

-include: origin collection info, description of item, each person to have custody (release/receive), date/time items were transferred

medical examiners

-commonly pathologists

-a medical examiner that specializes in the nature and causes of disease

Forensic Pathologist

-determines cause and manner of death in unexplained/unnatural deaths

-completed a medical degree

-clinical training in pathology

-pass an exam by the American Board of Pathology

Coroner

-qualifications vary across states

-not usually required to be a physician

-investigates deaths

-DOES NOT perform autopsies

-determines cause of death

-death certificates

-appointed or elected

-not required to be a forensic pathologist

Medical examiner

-Almost always required to be a physician

-investigates deaths

-performs autopsies

-determines cause of death

-death certificates

-appointed

-almost always a forensic pathologist

major duties during a death investigation

-confirm/pronounce death

-photograph/recognize/collect evidence from body

-perform a superficial body examination

-document postmortem changes (especially those associated with TOD)

-establish descendent identification and notify next of kin

-ensure security of remains

-autopsy

bags often used to hold skin

-this prevents skin from coming off the body as decomp begins

Role of forensic pathologist

-cause of death (medical determination): disease or injury that cause a physiological disruption that results in death

-manner of death (gov’t classification): homicide, suicide, natural, accidental, unknown/undetermined

-time of death

postmortem interval

-Temperature dependent

-Early (physico-chem changes): algor mortis, livor mortis, rigor mortis, ophthalmological changes, vitreous humor chemistry

Medium (entomology): decomposition, entomology

Late (anthropology): botany, anthropology, odontology

Taphonomy

-the study of processes by which organic remains pass from the biosphere into the lithosphere as the result of geological and biological processes

-anything that can happen to the body post death

natural physical/chemical changes

-most reliable in first 24 hours post mortem

-used to estimate time 

-pallor mortis, algor mortis, livor mortis, rigor mortis

-potassium content of eye

-all occur in the fresh decomposition stage (everything before bloating)

-all affected by temperature

Pallor mortis

-paleness of death

-develops in 15 minutes

-due to loss of blood circulation

Algor mortis

-metabolism generates heat (homeostatic mechanism)

-upon death the body cools

Algor mortis nomogram

Multiply body mass by correction factor, then use nomogram (changes rate based on layers of clothes, and if in water)

Livor mortis

-discoloration that occurs as blood pools

-diverts blood from pressure (white spots)

-generally .5-2 hours postmortem

-can provide info on corpse movement 

-set 6-8 hours postmortem (blood no longer moves)

Rigor mortis

-stiffening of body

-3-4 hours after death, persists ~12 hours

-occurs in all muscles simultaneously but may be noticeable first in smaller muscles

details of rigor mortis

-sarcoplasmic reticulum controls calcium levels in the muscle tissue

-after death sarcoplasmic reticulum becomes “leaky”

-stops making ATP and can’t “let go”, causes contraction

Potassium content of the eye

-vitreous humor: maintains eye shape/structure (extracellular fluid)

-has low potassium content and maintained in life by pumps

-after death pumps stop, membrane is leaky, and potassium moves down its concentration gradient

Decomposition stages

-fresh

-bloat

-active decay

-advanced decay

-dry remains/skeletonization

bloat stage

-autolysis: self digestion (enzymes) especially after lysosomes breakdown

-increased microbial activity

-both release gases

-bigger animals boat faster

decay

-putrefaction

-body collapses and gas escapes

-adipocere can be formed during the breakdown of lipids (can halt decomposition)