MEDT240 Exam #2 (Final Exam)

Impression evidence: bitemark collection and analysis

**Swab for DNA from saliva and epithelial cells

Impression evidence: bitemark types

**Two main types of bitemark impressions: Antemortem-less distinctive. Photograph for several days. Postmortem-well-defined , no bruising.

Patterns and descriptions

*It is ok just to describe a pattern a pattern and document it properly (just call it a unknown pattern)

Spatter stains are made up of

small circular and elliptical shaped stains,

Putrefaction typically manifests itself in:

the abdomen

External ballistics is conducted by

the crime scene analyst most often, may involve the firearms examiner.

Trajectory kits are used to evaluate bullet holes using:

trajectory rods. centering guides (cones). angle finders (protractors)

Impact Spatter Pattern Size of Stain

varies with speed of blood at time of impact.

Flies will begin laying eggs on an exposed corpse

within 20 minutes of death.

Rules for determining directionality of wipes and swipes

-Blood dries in the direction of travel and becomes "gritty". -Volume is displaced (pushed) in the direction of travel

first DNA fingerprint discovery:

1984, England, Sir Alec Jeffreys discovered first DNA "fingerprint"

Rigor appears within

2 hours of death, becoming greatest at 8-12 hours after death. It will disappear within 24-48 hours after death.

Bleeding suspects often deposit:

90 degree angle (circular) blood drops

Fiber transfer fact

90% of fiber transfers lost in first 8 hours.

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. Transfer stain in motion.

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. A preexisting volume of blood Dried outer ring (skeleton) of the original stain. Feathering, striations, diminished volume.

Individual characteristics

A trait or characteristic that allows the item to be compared to an individual item or person.

Class characteristics

A trait or characteristic that allows the item to be compared with another group of items and included or excluded in the group.

Bodies as "evidence"

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

Trace evidence: Soil (collecting)

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

Body temperature is highly variable, important factors include:

Ambient environmental conditions Body habitus (e.g., thin or fat)

exit wounds

CONFIGURATION of wound differentiates entrance from exit wounds Irregular borders.

Use of Luminol detecting Bloodstain Patterns

Checking scenes of suspicious disappearances for indications of clean-up

forensic pathologist ranges:

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.

Internal Ballistics

Conducted by the forensic firearms examiner at the crime lab.

Blood Flow

Follows gravity. Can indicate that an object was moved while the blood was flowing.

exit defects of bullets

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

DISCHARGED CARTRIDGE CASE PATTERNS (in relation to suspects)

IF SUSPECT'S GUN IS LOCATED, CONDUCT EJECTION PATTERN TESTS SAME GUN, SAME AMMO

bullets and kenetic energy

INCREASES IN BULLET VELOCITY HAVE GREATER EFFECT ON KE THAN INCREASES IN BULLET MASS.

class characteristics and guns significance

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

Packaging objects of evidence

If packaging object, package objects separately. NEVER package known material with evidence.

Decomp major factors

Major factors include environmental conditions, including temperature and humidity.

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.

close range contact wounds

May have Stippling

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.

Vacuuming trace evidence is the

Most improperly used method because it often results in the collection of a lot of irrelevant material.

Impression evidence: Footwear Patterns/general facts

Number of suspects Paths to and from the crime scene Easily damaged by weather, people, and vehicles - take immediate action to preserve

Body positioning after death

Once "fixed" a change of body position will not result in alteration of the livor mortis patterns.

Shooting defects:

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

They lay the eggs in and around ____ openings:

moist, including: Nostrils Corner of the eyes Mouth Open injuries Any other opening that is exposed

Gunshot residues (positive vs. negative)

Positive is not proof of firing. Negative is not proof of firing.

Expectorate Pattern

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

Trace evidence and nature

Primarily Class and occasionally Individual Characteristics

Trace evidence: Soil characteristic

Primary environmental unique characteristic is plant pollen.

Blowback from the rear of the gun consist of:

Primer Lead Barium Antimony

Seminal Fluid (semen)

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.

Photography of Bloodstain Evidence

Provides a non-invasive examination method Provides documentation that can be used by others at later date

Impact Spatter Pattern (smaller stains)

Related small stains with consistent directional angles. Radiating from a central point.

Impression evidence: tires

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

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.

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.

DNA Evidence Collection Kits

SANE Kit Suspect Rape Kit Buccal Swab Collection Kit

Preserving fiber evidence

Sheets of paper - on top of surfaces that have to be folded. Adhesive lifts - used for bodies "Druggist fold" - single hair or fiber

Two primary categories of bloodstain pattern taxonomy:

Spatter and Non-Spatter stains

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 typically manifests itself 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.

intermediate range contact wounds

Tattooing Abrasion Collar No Soot

Determinants of the extent of transfer are:

The intensity, duration and nature of materials in contact

Decomposition is

The most common aspect is the normal decomposition.

Medium velocity patterns

patterns that have stains that are predominantly between 1 and 4mm in diameter

High velocity patterns

patterns that have stains that are predominantly less than 1mm in diameter

Livor Mortis (lividity) is caused by

settling of the blood (as a result of gravity) in the small vessels of the circulatory system.

Absence of normal life signs

The presence of any combination of these conditions is not taken as presumptive evidence of death and may warrant life-saving

BPA Principles 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

External Ballistics are

The unpowered free-flight phase of the bullet after it exits the barrel and before it hits the target.

BPA Principles Pattern Diversity Principle

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

Insects on post mortem life cycles:

The various insects involved in this activity have defined life cycles, which if properly noted may assist in defining the post mortem interval.

Satellite Patterns

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

Assessment of bodies

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

Range of fire contact wounds

Tight or Loose: Seared Skin Triangular Tears Soot Muzzle Contusion ( Muzzle Stamp)

ANGLE OF INCIDENCE (ANGLE OF IMPACT)

USE ACUTE ANGLE... MUST USE A DIRECTION (LEFT/RIGHT, FRONT/BACK)

Types of Collection for trace evidence

Visual Inspection Tape Lift Vacuum

Blood Pool

Without any specific shape, but conforming to the surface contours. Collect White blood cells for DNA analysis.

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.

The primary insects of interest include:

Blow flies Beetles Wasps

Biological Evidence collection

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

Locard's Theory of Exchange

Every contact leaves a trace.

Rifled Barrel

Lands and grooves twist down length of gun

Impression evidence: Tool Marks

These unique marks can be as individual as fingerprints.

guns and acceleration

UP TO A POINT, THE LONGER THE BARREL, THE GREATER THE ACCELERATION.

Algor Mortis is

a loss of body heat in the corpse.

DISCHARGED CARTRIDGE CASE PATTERNS

are unreliable

Disposable / Non-Disposable forceps

clean with bleach

non-spatter stains are

everything else.

Cartridge Parts

CARTRIDGE CASE PRIMER POWDER CHARGE BULLET/PROJECTILE

DNA and CSI databases

CODIS - Combined DNA Index System. Central repository database

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 Case Individual Characteristics:

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

DNA and trace evidence

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.

After identifying a suspect four findings of bitemark examination:

Definite - to the exclusion of all others (i.e., only the suspect could have made the bitemark impression) Consistent - no features present that will exclude the suspect Possible - due to nature of injury, unable to positively confirm or exclude the suspect Exclusionary - definitely not made by the suspect.

Transfer Patterns Description

Demonstrating demarcations, curves or other recognizable characteristics of an object.

bodies and photographs

Detailed photographs of all aspects of the body, both in-situ and once rolled over.

Touch DNA

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

Detailed examination of the body entails:

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.

BPA Principles 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 Spatter and velocity

Important: Do not think of impact spatter as being related to specific velocities.

Impression evidence: Footwear forms:

Impressions - Prints - may not be able to physically recover

Livor mortis patterns may help the investigation:

In recognizing subsequent manipulation of the body after death (e.g., when the pattern is inconsistent with final position)

Trajectory analysis involves three areas of related ballistic study. These are:

Interior or internal ballistics Terminal ballistics. Exterior or external ballistics.

Spatter and events

It is important not to quickly associate the patterns with the common events that cause them.

Spurt Pattern

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

What is trace evidence?

Loosely defined, trace evidence is small evidence used to link victims, suspects, objects, and crime scenes.

Trace and hair fibers collection General Collection -

adhesive tape, 8-10 inch strips applied to item or area repeatedly. Don't over use tape on multiple objects or areas. Use an ALS when searching for fibers.

By observing and collecting the various stages of flies present on the body and in the scene,

an entomologist may be able to estimate the post mortem interval.

Elements of a blood stain

big portion is the parent stain tail points in the direction of travel ridges coming off the end are scallops droplets that are removed from the bigger stain are called satellite stains

Serological/Biological Evidence

blood or body fluids: spittle semen bone/tissue vaginal secretions

Trace and hair fibers collection Visible:

collect immediately. Seal in paper container. It won't be there later!

Directionality

defines the direction a droplet was moving at the time it struck a surface. Tail Points in the direction of travel.

Mechanical Fit

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