CSI Final Exam

Two Dimensional Impressions

- An impression having only the two dimensions of width and length. - Usually in indoor crime scene and many times found on the floor leading from the point of entry. - whole footwear tread does not have to be present to establish an identification. - Always collect the entire two-dimensional impression.

Examination-Quality Photographs

should then be taken to obtain maximum detail for forensic examination. • Shows impression as it was at the crime scene with any rocks, sticks or other debris which may be in, around or part of the impression • Shows the condition and detail of the impression • In some instances, such as with impressions in extremely coarse surfaces, photographs may represent the impression better than a cast • Backs up casting

Precipitin test

test that distinguishes between human and animal blood

where is the most bacteria

the gut

The longer the body is exposed and decomposes, ???

the more likely artifacts (evidence) will be disassociated to the remains.

tests for DNA, gunshot residues, bloodstains, varied particulates and residues are generally performed where

the morgue paper bags are placed on the hands at the scene to protect these important potential materials.

Point of Convergence

the most likely point of origin of the blood that produced the bloodstains

Swipe Pattern

the transfer of blood from a moving source onto an unstained surface; the direction of travel may be determined by the feathered edge

Assessment of body

verifying death based on following observations: Evident trauma inconsistent with life Absence of normal life signs

Adipocere

where the tissue becomes wax-like

Mummification

where the tissue dries out and mummifies.

Blood Flow

• An accumulation of blood. • With generally regular margins. • Leading from one point on a surface to another

Bodziak's Guide to Examination Quality Photography- Prepare Impression

- Place an L-shaped or long straight flat ruler alongside the length of the impression. - If its a 3D impression, carefully position the ruler on the same plane (level) as the bottom of the impression. - Include a label on the ruler to link this impression to the identifier number used in the general crime scene photographs and notes, as well as in subsequent casts or lifts.

Scattered Remains

- Surface remains scattered over a wide area prove more difficult than a grave. - A line search is usually the most effective search pattern.

Livor Mortis

- The pooling of the blood after death from gravity resulting in a reddish color to the skin - may appear in as little as 30 minutes following death and generally becomes fixed within 8 hours of death. - Once "fixed" the red will remain in same location and not turn white once pressed on - It may assist the Medical Examiner in determining the postmortem interval (time since death).

Three Dimensional Impressions

- defined by three separate measurements: width, length and depth. - can be found indoors in flour, sugar, dust, fire extinguisher propellant, etc., but are more often encountered in the outdoor crime scene in sand, mud, clay or snow.

Rigor Mortis

- stiffening of the muscles caused by a chemical reaction in the muscles as they break down after death. - manifests itself first in smaller muscles (e.g., jaw and face). - Appears within 2 hours of death, becoming greatest at 8-12 hours after death. will disappear within 24-48 hours after death due to decomposition. - may assist the Medical Examiner in determining the postmortem interval (time since death).

Problems Associated with Fire Scenes

- structural stability - Lighting - photo quality

Casting Materials Requirements (9)

1. Capable of reproducing very fine detail. 2. A viscosity that will allow even flow into the impression but not be absorbed by it. 3. Able to be cleaned without loss of detail and should release itself from the material in which the impression was made. 4. Reasonable in cost. 5. Easily obtainable in a consistent form and quality. 6. Easy to mix and use, even under adverse conditions. 7. Exhibit a reasonable "set" time, be durable, and have dimensional stability. 8. Not require special equipment or complex procedures. 9. Not have a limited shelf life.

The presence, characteristics and conditions of the impressions can assist in determining (4)

1. Number of suspects involved 2. Their path through and away from the crime scene 3. Their involvement in the crime 4. Events that occurred during the crime.

Grave Site Methodology

1. Set a datum point and grid to map the scene and artifacts to. 2. Locate, document, map and recover all surface artifacts. 3. Loose debris is removed to the level of the obvious fill dirt. a. Examine the area with a metal detector, flag any hits. 4. Cut ground plants at the surface, so as not to disturb the fill. 5. Fill dirt is removed carefully from the entire surface, using small trowels. a. As artifacts are located, they are documented, mapped and recovered. b. Each layer containing an artifact or a change in fill dirt is treated as a significant layer. 6. The dig is kept in phase, where the entire layer is removed, to prevent disturbing lower layers. 7. Once body is fully exposed, the remains are documented, mapped and recovered. 8. Articles or marks may exist in the bottom of the grave. a. Grave is excavated to the bottom and all fill dirt removed. b. Look for shoe marks, tool marks and other artifacts. c. Use a metal detector on the grave bottom (e.g. possible bullets fired into the grave) 10. Screen/Sieve all fill dirt removed from the grave.

Flies will begin laying eggs on an exposed body within _____ minutes of death.

20

Luminol

A chemical that emits a blue glow when it comes in contact with blood - Area being examined must be completely dark. - extremely sensitive - can detect bloodstains diluted to 1 in 100,000 parts.

Drip Trail

A series of related in-line drops falling from an individual or object. Directionality of the individual stains may define the direction the individual or item was moving at the time.

6 STEPS OF INVESTIGATION

ASSESS OBSERVE DOCUMENT SEARCH COLLECT ANALYZE

Collection and Preservation of Arson Evidence

Airtight Packaging- Clean paint cans

Defining Area of Origin

Combining point of convergence and impact angle for a number of stains leads to the Area of Origin for the pattern.

External Ballistics

Conducted by the crime scene analyst most often, may involve the firearms examiner. Involves defining the path of a bullet through the scene by evaluating various scenes aspects, such as penetrations and perforations, cartridge cases and known positions of the victim or shooter. Ultimately it defines possible and impossible scenarios for bullet trajectories.

Internal Ballistics

Conducted by the forensic firearms examiner at the crime lab. Involves function and operation of the weapon, association of weapon, bullets and cartridge cases. Often involves evaluation of ejection patterns and gunshot residue range (distance) determinations.

Wound/Terminal Ballistics

Conducted by the forensic pathologist. Involves defining the path of a bullet through the body, the associated damage and differentiating entry from exit wounds. Also includes issues of range (distance) determinations.

PAB (Physically Altered Bloodstain) Principle

Exposed blood will react to environmental conditions (e.g., air flow, temperature, humidity, variations of surface) in a predictable manner.

V-Patterns

Fires generally burn in a direction of up and out producing an apparent V-pattern at the fire scene. This pattern can assist in determining flame flow and the point of origin at a fire scene.

what is often destroyed by first responders

Footwear and tire tread impression evidence

Range (Distance) Determinations

Forensic firearm examiners use the weapon and similar ammunition to create gun powder residue standards at different distances to compare to the questioned residue patterns.

General Crime Scene Photograph Quality

General crime scene photographs (overall, midrange, and closeup) should be taken to relate the impressions to the crime scene.

Which presumptive blood test is excellent for latent or hidden blood and blood patterns?

Luminol test and Blue Star

Evident trauma inconsistent with life may include

Major head trauma (clear disruption of the brain) Decapitation Exsanguination - Massive blood loss Presence of decomposition

confirmatory tests for blood

Microcrystalline tests - Takayama and Teichmann

Will bloodstains fluoresce under Ultraviolet (UV) light?

NO bloodstains will absorb all light making the stains appear dark or black.

Grave Site Identification (Intrusive & Non Intrusive)

Non-intrusive means involve visual recognition and technology (e.g. ground penetrating radar, magnetometers). Intrusive means involves probes and vapor monitors.

Impression Evidence

Objects or materials which have retained the characteristics of other objects or materials which have been impressed against them.

Bodziak's Guide to Examination Quality Photography- Use Oblique Lighting

Oblique lighting should be used in most instances for both two-dimensional and three-dimensional impressions, as it provides better contrast.

Prime objective in any fire scene investigation

Origin and Cause - Defined by examining fire signs.

Gunshot wound classifications

Penetrating - bullet enters but does not exit. Perforating - bullet enters and exit. Grazing - bullet skims across the external aspects of the tissue but does not enter the body Tangential - bullet skims across the body producing a series of shallow wounds that penetrate to the subcutaneous tissue.

Fire patterns (3)

o Char Patterns o Smoke and Soot Patterns o Damage Patterns

Ranges for evaluating physical characteristics of a wound (5)

o Close contact - pressed to the skin. o Loose contact - close proximity to the skin, small gap. o Near Contact - not more than five inches from the wound. o Intermediate Range - 5 - 40 inches from the wound. o Indeterminate Range - no characteristics, so no conclusion.

Trajectory Kits

Primary concern of external ballistics is evaluating bullet defects. Trajectory kits are used to do this, they include: o Trajectory rods. o Centering guides. o Angle finders. o Lasers (in some cases).

Landfill Search Methodology

Remove the trash in an orderly fashion, one or two buckets at a time. - Observers watch the removal of each bucket.

If no ME or ME Investigator is on scene, the crime scene investigator has an absolute responsibility to:

Respect the ME's authority and not touch or alter the body without permission. Capture appropriate scene context and share that with the ME, to assist them in establishing the cause and manner of death.

The two typical forms of sharp force

Stab - a wound which is deeper than it is long. Incised wound - a wound which is longer on the skin surface than it is deep.

Putrefaction typically manifests itself in the abdomen as

Swelling of tissues Black or blue discoloration of tissue Protrusion of the eyes or tongue Ultimately resulting in slippage of skin and purging of fluids.

Gunshot entry wounds tend to be:

Symmetrical (circular or elliptical) Surrounded by an abrasion ring

Algor Mortis

The cooling of the body after death Body temperature is highly variable, important factors include: Ambient environmental conditions Body habitus (e.g., thin or fat) estimating the postmortem interval (time since death).

Casting

The filling of a 3D footwear or tire impression with a material that will take on and retain that impression. • Gives life-like and actual-size molding of the original impression including uneven surfaces and depths • Gives reproduction of microscopic characteristics • In deep impressions, gives reproduction of characteristics of the sides of outsoles and midsoles of the shoes which are usually not reproduced in photographs • Never a focus or scale problem • Provides tangible 3-dimensional evidence • Backs up photography

ABA HemaTrace

The method of choice today is test strips - Determines stains to be identified as Human Blood. extensively validated and shown to be sensitive, specific, and rapid. antigen/antibody reaction test

Directionality

o Defines the direction a droplet was moving at the time it struck a surface. o (for blood) Defined by both the long axis of the stain and the presence of scallops, tails, and satellite spatter. These appear in greater concentration on the side opposite where the droplet first struck the surface.

Basic casting and lifting techniques for impression evidence (4)

o Plaster and Dental Stone - 3-dimensional impressions. o Gelatin and Other Adhesive Lifters - 2 dimensional impressions. o Rubber Casting - tool marks. o Electrostatic Lifting Devices (ESLD) - dust prints.

Bluestar

produces light (luminescence) rather than color. - Area being examined does not have to be dark. - extremely sensitive - can detect bloodstains diluted to 1 in 100,000 parts.

Char Patterns

result from direct flame involvement. may involve deep charring of wall studs or more subtle charring from heat convection on exterior surfaces. can help demonstrate the relative time a surface was burning when compared to similar surfaces.

The Principle of Stain Shape and Vector Correlation

The shape of a bloodstain provides indicators as to the direction of deposition as well as the spatial origin of the blood. Sub principles are: • Impact • Directional Angle • Area of Origin

Pattern Diversity Principle

The variations in combinations of blood volumes and forces acting on those volumes lead to recognizable classes of patterns.

Mathematical Calculation of Bullet Impact Angles

There is an empirical relationship between the shape of the bullet defect and the angle of the bullet's impact into the target. By examining the bullet hole and measuring the long and short axes of the defect, one can apply a trigonometric formula to define the bullet's angle of impact

Tumbling

Tumbling bullets often create distinct characteristics. Obvious tumbling eliminates any ability to evaluate impact angle.

Bodziak's Guide to Examination Quality Photography- The Camera

Use a professional DSLR (Digital Single-Lens Reflex camera set at its highest resolution.

Gelatin and Adhesive Lifters

Used on 2-dimensional impressions

How to verify the defect is a bullet hole

Visual examination. Presence of bullets or remnants. Chemical presence of lead or copper. Awareness of any trace materials that may be in the bullet hole

Deflections or Ricochet

When the bullet strikes a surface and deflects off it at some angle without penetrating the surface completely The bullet itself may show indications of the angle at which it deflected

Impact Angle Formula

Width / Length = N (N always less than or equal to 1) Inverse Sine of N = Impact Angle

Wipe Pattern

a bloodstain pattern created when an object moves through an existing stain, removing it or changing its appearance • Displaced blood from the original boundary. • Dried outer ring (skeleton) of the original stain. • Feathering, striations, diminished volume.

hypoxia

a lack of sufficient oxygenated blood entering the brain Rarely is the actual airway occluded.

Mechanisms of Injury

Asphyxial injuries Sharp force trauma Blunt force trauma Gunshot/Shotgun wound trauma

Fire Scene Methodology

Assessment always begins on the exterior of the scene, if possible include an elevated viewing. Both assessment and observation are conducted from the least damaged area to the most damaged area. This makes it easier to understand what the investigator is seeing once they begin evaluating heavily damaged areas (e.g. comparing the nature of surfaces and materials observed in the less damaged areas to the debris in the heavily damaged area). Examine all fire signs independently. This often involves significant excavation activities. Always look for evidence of low burn.

Gunshot exit wounds tend to be:

Asymmetrical and irregular Lack soot and stippling Exception is the "shored" exit wound.

Presumptive Blood Testing

Based on peroxidase-like activity of the hemoglobin o Benzidine color test o Phenolphthalein (Kastle-Meyer) color test o Hemastix

The morgue offers

Better lighting and environmental conditions. Better position of the body for continued photographic documentation and examination (e.g., on the examination table versus some odd position in the scene)

Theory of Bloodstain Pattern Analysis

Blood as a fluid responds to forces in a predictable manner. The principles employed are: • Pattern Diversity Principle • Correlation of Stain Shape and Vector Principle • PAB (Physically Altered Bloodstain) Principle

Blunt Force Mechanisms of Injury (3 types)

Blunt force involves crushing and tearing of the skin and tissue. Contusions (bruising) - blood escapes into surrounding tissue resulting in discoloration. Abrasions - minor damage to the outer layers of skin; scraping injuries Lacerations - a physical tear of the tissue, creating an irregular margin wound with tissue bridging.

gunshot wound distances (4)

Contact - the muzzle of the weapon is pressed against the body resulting in soot and gasses entering the wound. Close Contact - the weapon is close enough for heat effects to occur to the skin. Stippling (powder driven into the skin) manifests itself around the wound. Intermediate - the weapon is far enough away that heat and soot effects are eliminated, and only stippling appears. Indeterminate - no heat, soot or stippling is noted, suggesting either a distance shot, or an intermediate object was between the weapon and the wound.

Effect of Target Surface (Smooth & Rough)

Effect of blood droplet falling on a smooth flat surface: drop spreads out evenly. Effect of blood droplet falling on a rough surface: Surface tension of spreading edge is broken by irregular surface (coronal appearance) along with microdroplets

Bullet Defect Characteristics (entry and exit)

Entry bullet defects generally have a symmetrical circular or elliptical aspect. Exit bullet defects generally have an irregular or asymmetrical shape. Material pushed out from the defect will suggest exit (e.g. showing the direction of travel of the bullet.

Authority Over the Body

In most jurisdictions, the corner/medical examiner (ME) or Justice of the Peace has absolute authority for the body.

Utilizing a Trajectory Kit

Insert the rod into a perforating defect. Use centering guides to level the rod in the defect. Angle finder used to document the angle of the trajectory. Documentation includes identifying the exact position of defects. o Each defect must be individually identified o Road mapping is a very good technique to utilize when documenting this type of evidence Over any distance, a laser attachment is used to demonstrate the trajectory. Does not interfere with trace evidence evaluations. Strings and other items stretched along the trajectory will sag and not be functional.

Trajectory Analysis

Involves three areas of related ballistic study: o Interior or internal ballistics o Terminal ballistics. o Exterior or external ballistics. - Each area of study is accomplished by different parties, but all are necessary to understand the scene.

Absence of normal life signs which include

Lack of a pulse in major arteries (carotid, femoral) Lack of a heartbeat, Lack of respiration Lack of evident body heat Lack of constriction of the pupils in response to light Lack of flushing in the nail beds Lack of movement or response to stimuli

The Sieving Process

Look for any evidence such as the items below: Bone, teeth, hairs, etc.; Fibers, string, cord, rope, buttons, etc. Paint, glass, plastics; Trash/paper items; Jewelry; Gum; Botanic Material Entomological Material Tool Components

Asphyxia

body is unable to take in oxygen and or eliminate carbon dioxide. Strangulation Smothering Choking Drowning Positional or mechanical asphyxia Chemical asphyxia

Primary mechanism of death

exsanguination (loss of blood).

Smoke/Soot Patterns

help demonstrate the development and flow of the fire.

Damage Patterns

indicate the flow of the fire in the scene.

Methodology of Bloodstain Pattern Analysis

• Familiarize yourself with the entire scene • Identify discrete patterns. • Categorize the patterns. (e.g. castoff versus impact) • Evaluate aspects of directionality and motion. • Evaluate points of convergence and area of origin. • Evaluate interrelationships of stains and other items. • Based on all of the above evaluate viable source events to explain the pattern. • Define a Best Explanation Given the Data. • Validate the conclusions (Peer Review)

Spurt Pattern

• Large volume evident in the overall pattern or individual stains. • The stains will present a linear or curvilinear orientation that may appear as a waveform with rises and falls. • Most often results when an artery or the heart is injured.

Expectorate Pattern

• Related non-linear spatter - wide range of size. • Presence of an airway injury or blood in an airway (nose or mouth) and one of the following: • Presence of vacuoles/air bubbles • Presence of mucous strands • Presence of epithelial cells. • Possible dilution of color (due to saliva).

Impact Spatter Pattern

• Related small stains with consistent directional angles. • Radiating from a central point. • Progressive change in shape of the stains the further out. • Various sized stains, but generally consistent throughout the pattern.

Blood into Blood Pattern

• Series of individual passive blood stains or a pooling of blood. • Surrounded by a random distribution of small spatter. • The spatter will generally not have consistent directional angles.

Castoff Pattern

• Series of related stains. • Linear or curvilinear in orientation • Consistent parallel directional angles. • Caused by blood-bearing objects (such as weapons, hands, clothing, etc.) being swung

Documenting Bloodstain Patterns

• Take standard overall photographs of areas (walls, floors) showing multiple patterns. • Take overall photographs of the extent of each discrete pattern. • Take detailed photographs of any individual stains that are used for "Point of Origin" determination or that show critical characteristics. • Use road mapping technique • Obtain serology/DNA samples from every significant pattern.

Electrostatic Lifting (ESLD)

• The ESLD captures dust prints of shoes and tires. •Used on almost any dry surface.

Information provided by footwear impressions

• Type: Athletic shoe, loafer, pump, etc. • Make: Nike, Reebok, Converse, etc.... • Description • Approximate or Precise Size • The location of the footwear impressions can help reconstruct the crime

Rubber Casting Compounds

• Used for impressions (toolmarks, etc.) on nearly any surface. • Special silicone materials capture microscopic details. • If possible, recover the actual impression as well.