Crime Scene Investigation Final

Bloodstain Pattern Analysis

  • Bloodstain pattern analysis

    • analysis of the location, shape, size, and distribution of bloodstains

  • Why do bloodstain pattern analysis?

    • To recreate the actions that caused the bloodshed

  • What does bloodstain pattern analysis provide for an investigation?

    • information about what happened and what could not have happened

  • Where to encounter blood evidence

    • On the victim, at the crime scene, on a weapon, on the assailant

  • Target surface

    • a surface onto which blood has been deposited

  • What is blood composed of

    • 55% plasma, less than 1% white blood cells and platelets, and 45% red blood cells

  • SWGSTAIN

    • Scientific Working Group on Bloodstain Pattern Analysis

  • What information does BPA reveal (9 items)

    • origin of blood drops

    • distance from origin to impact

    • direction of the impact

    • type of impact

    • number of blows, stabs, or shots

    • position of the victim/assailant at time of bloodshed

    • movement of victim/assailant during bloodshed

    • movement of victim/assailant after bloodshed

    • corroborate statements from the witnesses

  • Surface tension

    • The cohesive forces exerted upon the surface molecules which pull towards the interior of the liquid to minimize surface area

  • what shape do blood drops form

    • spheres

  • If a free-falling drop of blood strikes a smooth surface, what is the resulting bloodstain pattern

    • a circular bloodstain

  • Increased distance falling of a blood drop results in what

    • increased diameter of the resulting bloof stain

  • Terminal velocity

    • maximum speed to which a free-falling drop of blood can accelerate in air

  • How does volume affect terminal velocity?

    • larger volumes of blood in a drop have higher terminal velocities

  • What happens when a drop of blood strikes a textured surface?

    • surface tension will rupture and the circle will distort and create spines along its edges

  • satellite stains

    • smaller bloodstains that originated during the formation of the parent stain as a aresult of blood impacting a surface

  • What angle does blood need to fall at to create a circular bloodstain?

    • 90 degrees

  • what happens when blood strikes a surface at an angle less than 90 degrees?

    • an elliptical bloodstain

  • the greater the angle, the ___

    • greater the elongation

  • directionality

    • the tail of the greatest distortion will point in the direction of travel

  • when measuring length of a bloodstain, what is not included

    • the tail of the stain

  • angle of impact equation

    • arc sin (width/length) in mm. answer in degrees

  • Types of bloodstains

    • passive, transfer, and projected/impact

  • Types of passive bloodstains

    • drip stain, drip pattern, pool

  • drip stain

    • a bloodstain resulting from a falling drop that formed due to gravity

  • drip pattern

    • a bloodstain pattern resulting from blood dripping into blood

  • pool

    • a bloodstain resulting from an accumulation of liquid blood on a surface

  • projected bloodstains

    • result from the ejection of a volume of blood under pressure/force

  • types of projected bloodstains

    • impact/spatter pattern, cast off pattern, expiration pattern, arterial gushing/spurting

  • impact pattern

    • resulting from an object striking blood

  • cast off pattern

    • from blood drops released from an object due to its motion

  • expiration pattern

    • from blood forces by airflow out of the nose, mouth, or wound; may see air bubbles, strings of life, or blood mixed with saliva

  • arterial gushing pattern

    • from blood exiting the body under pressure from a breached artery

  • types of transfer bloodstains

    • transfer/contact, swipe, wipe

  • transfer/contact

    • from contact between a blood-bearing surface and another surface without motion

  • swipe

    • from the transfer of blood from a blood-bearing surface onto an unstained surface with motion

  • wipe

    • an altered bloodstain resulting from an object moving through a preexisting bloodstain

  • voids

    • an absence of blood in an otherwise continuous bloodstain

  • When is the stringing method conducted

    • after documentation, before blood evidence collection

  • area of convergence

    • the area containing the intersections generated by lines drawn through the individual axes of stains that indicate, in two dimensions, the location of the blood source

  • area of origin

    • 3D location from which spatter originated

Trajectory Determination

  • What is required for accurate bullet trajectory reconstruction

    • two bullet defects (holes or impact sites)

  • Why is the trajectory determination done?

    • to determine bullet path

    • determine shooter’s position

    • determine likely location of bullets

    • can eliminate shooter’s position

  • zone 1 of possibility

    • the area of greatest probability that is at or lower than the likely shooter’s shoulder height in a comfortable position

  • zone 2 of possibility

    • includes possible locations where a shooter could have been when the shot was fired which would entail an awkward stance or position

  • zone 3 of possibility

    • includes areas within the identified shooting area that would be impossible for the shooter to have stood and fired the shot

  • how does angle of impact affect bullet holes

    • may elongate the bullet hole, cause the bullet to become damaged or tumble to make different shapes of hole

  • entry defect

    • regular margins

  • exit defect

    • irregular margins with surface material pushed out, forming a crater in the direction of travel

  • What do trajectory kits include

    • trajectory rods, protractor and angle finder, spacer cones and o-rings, string or lasers, and photographic fog

  • which is more accurate for long distances: strings or lasers?

    • laser trajectory is more accurate for longer bullet path distances

  • how to measure the entrance hole

    • vertical distance from the floor

    • horizontal distance from the left or right wall

  • how to measure the exit hole

    • vertical distance from the floor

    • horizontal distance from the same wall/edge as the entrance hole

  • angle of impact calculation for trajectory determination

    • arcsin (width/length) on mm, answer in degrees

  • FARO focus 3D scanner

    • uses calibrated trajectory spheres to accurately determine bullet path

  • victim wound bullet trajectory

    • may help determine position and location of victim

  • wall scope

    • used to recover bullets/fragments behind walls with minimal damage

Human Remains Recovery

  • Forensic pathology

    • study of sudden, unexpected, suspicious, or unnatural deaths

  • what are important factors of a death investigation (5 items)

    • coroner or medical examiner must be notified

    • body should not be moved until all relevant info/documentation has been gathered

    • ME performs autopsy to determine cause and manner of death

    • estimate the post mortem interval

    • determine the identity

  • forensic anthropology

    • works with a forensic pathologist/odontologist to identify human skeletal remains, collect them, build an anthropological profile, determine the cause and manner of death, identify the deceased, and estimate the post mortem interval

  • forensic odontology

    • identification of the deceased through age, trauma, and bite mark analysis

  • facial reconstruction

    • drawing renditions, clay reconstruction, and computer aidied reconstruction

  • taphonomy

    • the postmortem history of the body

  • what does taphonomy include

    • decomposition stages

    • interpretation of trauma

    • evidence of scavenger modification

    • insect activity

    • weathering/environmental factors

    • modification by water, botany, or geology

  • Types of burial indicators

    • disturbed vegetation

    • soil compaction

    • new vegetation

    • soil disturbance

  • Factors that affect burial indicators

    • time since burial, ground moisture, terrain

  • tools used in searching for human remains

    • aerial/visual, infrared/thermal photography, metal detector, cadaver dogs, probes, GPR

  • search area

    • a large area that is searched when investigators don’t know where the remains are located

  • recovery area

    • only the area containing the burial or surface remains

  • sequence of an excavation

    • search, place stakes around perimeter to string a grid, systematically remove the ground and soil layer by layer to excavate, document every bone or item found in a layer, collect soil and insect samples, remove the remains and lay out into body bag, search soil beneath the body

  • why are sifting stations used

    • to make sure nothing was missed during troweling

  • Scattered remains recovery method

    • detailed line search on hands and knees with buckets

Forensic Entomology

  • forensic entomology

    • the study of insects and related arthropods involved in legal issues

  • what scope does FE have

    • involved in investigation of death, abuse, and neglect cases

  • what can FE be used to determine

    • climate and temnperature conditions at death

    • location and movement of body

    • location of antemortem injuries

    • submerging of body in water

    • presence of drugs in bodies

    • recovery of human DNA from digestive tract

  • Life cycle of blowfly

    • upon death of person, slies arrive and lay eggs in moist openings

    • day 2 the eggs hatch and larvae emerge

    • days 3-7 larvae eat and grow

    • days 8-9 prepupation in which larvae form hard, cocoonlike shell and begin to develop adult features

    • two weeks, a fully developed adult fly emerges

  • insect succesion during decomposition process

    • fresh (1-2 days) adult blowflies, flesh flies, yellow jackets

    • bloated (2-6 days) blowflied and other flies, beetles, yellow jackets

    • decay (5-11 days) some flies and beetles, cockroaches

    • post decay (10-24 days) beetles, fruit flies, gnats, and some other flies

    • dry stage (24+ days) some beetles, ants, and flies

  • entomological evidence collection steps

    • observations of scene and body, as well as insect activity

    • weather data

    • collection of specimens from body

    • collections of specimens/soil from surrounding area

    • collections of specimens/soil from under body

    • collection of specimens during autopsy

    • ship specimens to a forensic entomologist

  • scene/body observations

    • scene habitat type

    • exact location of scene using GPS

    • orientation and position of the body

    • presence of clothing or wrappings

    • decomposition stage of body

    • note trauma, burning, or dismemberment

    • location of the body in relation to vegetation

    • location of the body in relation to doors or windows

    • sun or shade conditions

  • insect activity observations

    • note species present

    • location of insect activity in the surrounding area

    • various life stages of each location

    • location of insect infestations on the body

  • weather data records

    • ambient temperature

    • humidity

    • temperature of body’s surface

    • temperature at the body/surface interface

    • temp of soil surface away from body

    • temperature of larval masses

    • temp of soil after body is removed

    • estimate duration of exposure to sun vs shade

    • obtain official weather data before and after body was discovered from National Weather Service Office