crime scene investigation

bite marks, cont.

***Provided a suspect is identified, four findings can be related to the examination of bitemarks Definite - Consistent Possible Exclusionary

Impression Evidence: Bitemark

**Swab for DNA from saliva and epithelial cells **Two main types of bitemark impressions: Antemortem-less distinctive. Photograph for several days. Postmortem-well-defined , no bruising.

Bloodstain Pattern Analysis

two primary categories of the bloodstain pattern taxonomy: Spatter and Non-Spatter stains 90 degree angle (circular) blood drops are often deposited by a bleeding suspect.

trace evidence methods of collection

1. Visual Inspection 2. Tape Lift 3. Vacuum: Most improperly used method because it often results in the collection of a lot of irrelevant material.

Trace Evidence

> Loosely defined, trace evidence is small evidence used to link victims, suspects, objects, and crime scenes > The intensity, duration and nature of materials in contact determine the extent of transfer > Primarily Class and occasionally Individual Characteristics

Successive Penetrations

A fracture always terminates at an existing line of fracture

Swipes

A pattern caused by a bloodstained object coming into contact through lateral motion with another object which is not bloodstained

Wipes

A pattern caused by an object coming into contact through lateral motion with a pre-existing bloodstain on another object. Can be distinguished from swipes by the presence of skeletionization of the original bloodstain. Blood dries in the direction of travel and becomes "gritty". -Volume is displaced (pushed) in the direction of travel

Algor Mortis

Algor Mortis is a loss of body heat in the corpse. Body temperature is highly variable, important factors include: Ambient environmental conditions Body habitus (e.g., thin or fat)

The Body as a Crime

Alive or dead, the body of the victim represents a significant scene that must be fully documented and processed.

Trace Evidence: Soil

Always collect soil, even if a definite crime scene has not been determined **Always collect control samples - top level of soil Tablespoon size Alibi locations Primary environmental unique characteristic is plant pollen. Standards Collect samples from multiple locations believed involved. Minimum of six from general area.

Use of Luminol detecting Bloodstain Patterns

Checking scenes of suspicious disappearances for indications of clean-up

Range Determinations

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

Biological Evidence

Collection: Collect entire item if possible, particularly clothing. Air dry thoroughly, before final packaging.

External Ballistics

Conducted by the crime scene analyst most often, may involve the firearms examiner. The unpowered free-flight phase of the bullet after it exits the barrel and before it hits the target. INCREASES IN BULLET VELOCITY HAVE GREATER EFFECT ON KE THAN INCREASES IN BULLET MASS.

Internal Ballistics

Conducted by the forensic firearms examiner at the crime lab UP TO A POINT, THE LONGER THE BARREL, THE GREATER THE ACCELERATION

Fly Activity

Flies will begin laying eggs on an exposed corpse within 20 minutes of death. They lay the eggs in and around moist openings:

exit defect

Generally have an irregular or asymmetrical shape

Trace Evidence: Glass

Generally yields only class characteristics - not individual characteristics Collect control samples to establish linkages - Hit and Run

impact splatter cont.

High velocity patterns that have stains that are predominantly less than 1mm in diameter Medium velocity patterns that have stains that are predominantly between 1 and 4mm in diameter Important: Do not think of impact spatter as being related to specific velocities.

Conclusions of analysis

If class characteristics and striations match, can say the bullet was likely fired by the suspect gun

ME and Investigator Relationship

If no ME Investigator is on scene, the crime scene investigator has an absolute responsibility to: Respect the ME's authority and not alter the body without permission Capture appropriate scene context and share that with the ME, to assist them in establishing the manner and cause of death.

Close Range:

May have Stippling

Mechanical Fit

Mechanical Fit is an individualization by fitting two or more pieces of something together:

Mitochondrial DNA (mDNA)

Mitochondria are present in greater number in every cell. mDNA however is not individual. It is shared in a family and follows the matriarchal line.

DEFECTS

PERFORATION DEFECT - GOING THROUGH SOMETHING. PENETRATION DEFECT - GOING INTO SOMETHING.

Impression Evidence: Footwear

Patterns: 1. Number of suspects 2. Paths to and from the crime scene Easily damaged by weather, people, and vehicles - take immediate action to preserve -- Two forms of footwear evidence: Impressions - Prints - may not be able to physically recover

Expectorate Pattern

Presence of an airway injury or blood in an airway (nose or mouth)

Seminal Fluid

Prostate-specific antigen (present in semen) - presumptive tests (this is a simple Field test for the presence of semen.) ALS can locate possible seminal fluid, followed by presumptive tests if you have sufficient samples.

Impression Evidence: Tire

Remove the vehicle from the SCENE and transport to a SECURE facility for processing

Transfer Patterns

Result from the transfer of blood from one object to another without an lateral motion. Stains will diminish in the direction of travel as a bloodstained object leaves transfer pattern repetitively (trail of footwear impressions)

castoff pattern

Result of an object which is motion, or suddenly stops.

Rigor Mortis

Rigor Mortis is caused by a chemical reaction in the muscles as they break down after death. It manifests itself as a stiffening of the muscle. Rigor appears within 2 hours of death, becoming greatest at 8-12 hours after death. It will disappear within 24-48 hours after death.

DNA Evidence Collection Kits

SANE Kit Suspect Rape Kit Buccal Swab Collection Kit

Tight or Loose contact

Seared Skin Triangular Tears Soot Muzzle Contusion

trace- fibers

Sheets of paper - on top of surfaces that have to be folded. Adhesive lifts - used for bodies "Druggist fold" - single hair or fiber 90% of fiber transfers lost in first 8 hours.

exit wounds

Size of wound does not differentiate entrance from exit wounds CONFIGURATION of wound does! Irregular borders.

spatter stains

Spatter stains are made up of primarily spatter stains and non-spatter stains. small circular and elliptical shaped stains, non-spatter are everything else.

Arterial Spurt

Spiked pattern, Similar to an EKG

Blood into Blood Pattern

Surrounded by a random distribution of small spatter. The spatter will generally not have consistent directional angles.

Putrefaction

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.

Intermediate Range:

Tattooing Abrasion Collar No Soot

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 and AO

Pattern Diversity Principle

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

Insect Activity

The various insects involved in this activity have defined life cycles, which if properly noted may assist in defining the post mortem interval. The primary insects of interest include: Blow flies Beetles Wasps

Satellite Patterns

These patterns arise from blood droplets that leave the parent stain by some degree of force.

Tool Mark Evidence

These unique marks can be as individual as fingerprints.

Assessment

This is accomplished is based on two general observations: Evident trauma inconsistent with life Absence of normal life signs

Trajectory Analysis

Trajectory analysis involves three areas of related ballistic study, internal ballistics Terminal ballistics. Exterior or external ballistics.

Danger of contamination

Wear double gloves. Change outer glove each time you touch a new piece of evidence.

Blood Pool

Without any specific shape, but conforming to the surface contours. It may demonstrate serum separation Collect White blood cells for DNA analysis.

CARTRIDGE

FOUR PARTS: CARTRIDGE CASE PRIMER POWDER CHARGE BULLET/PROJECTILE

The morgue offers:

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

Cartridge Markings

Breech face marks Firing pin impressions Chamber marks Extractor marks Ejector marks

DNA Evaluations

Building block of life, present in every cell nucleus. No two DNA samples are the same (except identical twins). 1984, England, Sir Alec Jeffreys discovered first DNA "fingerprint CODIS - Combined DNA Index System

trace-- hairs

DNA from the follicle or mDNA may allow a more defined analysis.

DNA Probative Value

DNA is very stable and can remain intact for many years.

Pattern Transfer

Demonstrating recognizable characteristics of an object.

Detailed Examination of the Body on Scene

Detailed photographs of all aspects of the body, both in-situ and once rolled over. Examination of the hands for evidence (e.g., DNA, gunshot residues, bloodstains Examination of the areas beneath the body, that were not exposed during early on-scene efforts.

Gunshot Residues

Determination is extremely limited. >Positive is not proof of firing. >Negative is not proof of firing. made up of: Primer Lead Barium Antimony

Touch DNA

Epithelial Cells Most prolific types of human cells Items can be processed for fingerprint impressions BEFORE being tested for DNA.

assessment cont.

Evident trauma inconsistent with life may include: Major head trauma (clear disruption of the brain) Decapitation Massive blood loss Presence of decomposition The presence of any one of these conditions can be taken as presumptive evidence of death.

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.

impact splatter cont cont

It is important not to quickly associate the patterns with the common events that cause them. It is ok just to describe a pattern a pattern and document it properly (just call it a unknown pattern)

Rifled Barrel

Lands and grooves, Lands and grooves twist down length of gun

Spurt Pattern

Large elliptical stains. Line of stains or overlapping stains oriented in Vs, arcs or serpentine patterns.

Livor Mortis

Livor Mortis (lividity) is caused by settling of the blood (as a result of gravity) in the small vessels of the circulatory system. Once "fixed" a change of body position will not result in alteration of the livor mortis patterns.

Serological/Biological Evidence

blood or body fluids found in spittle semen bone/tissue vaginal secretions

Impact Spatter Pattern

consistent directional angles. Radiating from a central point Size of stains varies with speed of blood at time of impact. High velocity impact spatter can be characterized by stains less than 1mm in diameter