Amber Dror 19/10/14

FORENSICS: TEST #2CORPUS DELICI:

“body of the crime” authorities must prove:

o that a crime occurredo that the person charged with the crime was responsible for the crime

top reasons for committing a crime:o moneyo revengeo emotion – love, hate, anger

source of evidence:o bodyo primary and/or secondary crime sceneo suspect(s)

CRIME SCENE TEAM: a group of professionals trained in a variety of special disciplines

o first police officer on the sceneo medics (in necessary)o investigator(s)o medical examiner (if necessary)o photographer and/or field evidenceo lab experts

CRIME SCENE INVESTIGATION: based on the scientific method, the Locard Exchange Principle, logic, and forensic techniques involves:

o recognition – scene survey, documentation, collectiono identification – classification of evidenceo individualization – comparison testing, evaluation, and interpretationo reconstruction – sequences events, reporting, and pressuring

PROCESSING A CRIME SCENE: isolate and secure the scene interview the first police officer at scene or the victim to determine what allegedly happened, what crime

took place, and how the crime was committed examine scene – identify possible evidence, point of entry, outline general layout of crime scene document the scene – pictorial record, rough sketch to demonstrate layout of the crime scene and to

identify the exact position of the deceased victim or other evidence within the crime scene search for evidence collect and package evidence, maintaining the chain of custody submit evidence to the crime lab for analysis

FIST OFFICER ON THE SCENE: A – assess the crime scene and assist the injured

D – detain the witness A – arrest the perpetrator P – protect the crime scene T – take notes

CRIME SCENE SURVEY: walk-through:

o performed by crime scene investigator, the first officer, and sometimes the lead detective purpose:

o mentally prepare a reconstruction theoryo note change in evidence (transient, conditional)o note environmental and weather conditionso note points of entry/exits, paths of travelo record initial observations (5W, H)o identify special needs within crime scene

DOCUMENTATION: notes: date, time, description, weather, description of crime, people involved, etc. photography: scene, surroundings, close-ups of evidence at different angles (any witness) sketches: date, time, scale, distance, names of investigators/victims/suspects videography: allows for narration (non-subjective), different perspectives

SEARCH METHODS: line or strip method: best in large, outdoor scenes; walking in straight lines across the crime scene grid method: basically a double-line search (two or more people overlapping separate line searches

forming a grid) ; effective, but time-consuming zone method: most effective in houses or buildings; teams are assigned small zones for searching wheel/ray method: several people moving from the boundary straight toward the center of the scene

(inward) or from the center straight to the boundary (outward); best on small, circular crime scenes spiral method: the investigator move in an inward spiral from the boundary to the center of the scene or in

an outward spiral from the center to the boundary of a scene; best used where there are no physical barriers

COLLECTING AND PACKAGING EVIDENCE: one individual should be designated as the evidence collector to ensure that the evidence is collected,

packaged, marked, sealed, and preserved in a consistent manner, maintaining the chain of custody each item must be placed in a separate container, sealed and labelled the most fragile evidence is collected and packaged first different types of evidence require specific or special collection and packaging techniques the body is the property of the coroner or medical examiner; collection of evidence on the body is done by

that department

PACKAGING: most items should be packaged in a primary container and then placed inside a secondary one

o pill bottles. vials, manila envelopes, and plastic bags are good for most evidenceo trace evidence may be placed on a piece of paper which is then folding a particular way called a

“druggist’s fold”

these are then placed inside other containers such as paper bags, canisters, packets, or envelopes, depending on the type and size of the evidence

CHAIN OF CUSTODY: there must be a written record of all people who have had possession of an item of evidence, beginning at

the time of collectiono the evidence container must be marked for identification o the collector’s initials should be placed on the sealo if evidence is turned over to another person, the transfer must be recorded

CRIME SCENE RECONSTRUCTION: stages:

o data collectiono hypothesis formationo examination, testing, and analysiso determination of the significance of the evidenceo theory formulation

THE MEDICAL EXAMINER AND THE CORONER: medical examiner: medical doctor, usually a pathologist, and is appointed by the governing body of the area

o responsibilities: identify the deceased establish the time and date of birth determine a medical cause of death determine the mechanism of death (the physiological reason that the person died) classify the manner of death (natural, accidental, suicide, homicide, undetermined) notify the next of kin

coroner: an elected official who usually has no special medical training

FINGERPRINT PRINCIPLES (3): fingerprint is an individual characteristic; no two people have been found with the exact same fingerprint

patter fingerprint pattern will remain unchanged for the life of an individual; however, the print itself may change

due to permanent scars and diseases fingerprints have general characteristic ridge patterns that allow them to be systematically identified

DACTYLOSCOPY: the study of fingerprint identification

o police investigators are experts in collecting “dactylograms”, otherwise known as fingerprints

FINGERPRINT CLASSES: ARCHES – 5% of people:

o ridges enter on one side and exit on the other side LOOPS – 60% of people:

o ridges enter on one side and exit on the same side WHORLS – 35% of people:

o consists of circles, more than one loop, or a mixture of pattern types

RIDGEOLOGY: the study of the uniqueness of friction ridge structures and their use for personal identification

o a fingerprint is made of a series of ridges and valleys on the surface of the finger the uniqueness of a fingerprint can be determined by the pattern of ridges and valleys as

well as the minutiae points minutiae point: point where ridge structure changes points of similarity/points of identification: points in which minutiae on two different prints match

o no international standard for the number of points required UK: minimum of 16 Australia: minimum of 12

RIDGE CHARACTERISTICS: fingerprints have minutiae points, which are points where the ridge structure changes

o useful in matching a fingerprint to a specific person

AUTOMATED FINGERPTING IDENTIFICATION SYSTEM (AFIS): a computerized system capable of reading, classifying, matching, and storing fingerprints for criminal

justice agencieso uses computer algorithms to mark all minutia point, cores, and deltas on the print, which are used

to find possible matches with fingerprints in the database

LATENT PRINTS: impressions left by friction ridge skin on a surface, such as a tool handle, glass, door, etc. (aren’t visible to

the naked eye – consist of the natural secretions of human skins and require development for them to become visible)

o most secretions come from three glands: eccrine: secretes largely water with both inorganic and organic compounds – most

important for fingerprints apocrine: secretes pheromones and other organic materials sebaceous: secretes fatty or greasy substances

Plain

Arch

Ridges enter on one side and exit on the othe

r side

.

Tented Arches Similar to the

plain arch, but

has a spike in the cente

r.

Spike or “tent”

L – Radi

al Loo

pR -

Ulnar

Loop

Delta

L – Ulna

r Loop R -

Radial

Loop

plain whorlcentral pocket whorl

double loop whorl

accidental whorl

development:o requires substances that interact with secretions, causing print to stand out against its background

powders – adhere to both water and fatty deposits; choose colour to contrast with background

iodine – fumes react with oils and fats to produce a temporary yellow-brown colour cyanoacrylate fuming method (super glue method) – “superglue” fumes react with water

and other fingerprint constituents to form a hard, whitish deposit ninhydrin – reacts with the amino acids in fingerprints and will produce a blue or purple

colour – silver nitrate – reacts with chloride to form silver chloride, a material that turns grey when

exposed to lighto prints may be collected by:

revealing them with a dusting of black powder and then lifted with a piece of clear tape fluorescent powder and UV lights to help them find latent prints on multi-coloured or dark

surfaces magnetic powder to reveal latent prints and works on shiny surfaces or plastic baggies or

containers

CRIME SCENE PERSONNEL: police officers are typically the first to arrive at a crime scene

o they are responsible for securing the scene so no evidence is destroyed and detaining persons of interest in the crime

the csi unit documents the crime scene in detail and collects any physical evidence the district attorney is often present to help determine if any search warrants are required to proceed and

obtains those warrants from a judge the medical examiner (if a homicide) may or may not be present to determine a preliminary cause of death specialists (forensic entomologists, anthropologists, psychologists) may be called in if the evidence requires

expert analysis detectives interview witnesses and consult with the CSI unit

o they investigate the crime by following leads provided by witnesses and physical evidence

CRIME SCENE: any physical location in which a crime has occurred or is suspected of having occurred

o primary crime scene: the original location of a crime or accidento secondary crime scene: an alternate location where additional evidence may be found

suspect: person thought to be capable of committing a crime accomplice: person associated with someone suspected of committing a crime alibi: statement of where a suspect was at the time of a crime

INVESTIGATING EVIDENCE: drug chemistry: determines the presence of controlled substances and the identification of marijuana trace chemistry: identification and comparison of materials from fires, explosions, paints, and glass microscopy: microscopic identification and comparison of evidence, such as hairs, fibres, woods, soils,

building materials, insulation, and other materials biology/DNA: analysis of body fluids and dried stains such as blood, semen, and saliva toxicology: tests body fluids and tissues to determine the presence of drugs and poisons latent prints: identification and comparison of fingerprint or other hidden impressions from sources like

feet, shoes, ears, lips, or the tread on vehicle tires

ballistics (firearms): study of bullets and ammunition through the comparison of fired bullets, cartridges, guns, and gunpowder patterns on people and objects

toolmarks: examines marks left by tools on objects at a crime scene or on a victim, such as a hammer used to break a door or a screwdriver used to pick a lock

questioned documents: examination of documents to compare handwriting, ink, paper, writing instruments, printers, and other characteristics that would help to indentify its origin

IMPRESSION EVIDENCE: objects that have retained the characteristics of other objects through direct contact

o impressions are created when one object is pressed against another material with enough force to leave an impression of the object

e.g. shoeprints, tool marks, tire tracks, bite marks, marks on a fired bullet several methods:

o 2-D: using photography – impressions may be dusted with fingerprint powder to be photographed or lifted with tape; may also be collected using an electrostatic dust lifting process

o 3-D: using photography and casting – involves using dental stone or a similar substance to preserve the dimensional characteristics of the print