forensic science introduction crime scene investigation

FORENSIC SCIENCE

INTRODUCTION

Crime Scene

Investigation

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Forensic Science

Definition: The application of scientific technology to supply accurate and objective information reflecting the events that occurred at a crime.

What does a Forensic Scientist DO???

1. Analyze physical evidence

2. Provide Expert Testimony

3. Provide training in the recognition, collection and preservation of physical evidence

Complex ReasoningIn Forensic Science

Deductive (reasoning from the general to the particular) and

Inductive Reasoning (reasoning from detailed facts to general principles)

Classifying Comparing and Contrasting Problem Solving Analyzing Perspectives Constructing Support Error Analysis

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The History of Forensic Science

Sherlock Holmes: a fictional character developed by Sir Arthur Conan Doyle; used a great deal of forensic detection

Mathieu Orfila: toxicology (the detection of poisons) Alphonse Bertillon: anthropometry (personal identification

through body measurements) Francis Galton: developed 1st fingerprint identification system Leone Lattes: determined methods of using blood type as a

means of identification Calvin Goddard: firearms examination Albert Osborn: document examination Edmund Locard: Developed the 1st police lab J. Edgar Hoover: director of the FBI: Organized the 1st FBI

Crime Lab in 1932

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Locard’s Exchange Principle

Whenever 2 objects come in contact with one another, they exchange some material (dust particles, hair, dead skin cells…)

Locard strongly believed that every criminal can be connected to a crime by dust particles carried from the scene

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Branches of Forensic Science

Physical science: Using chemistry, physics, and geology to ID and compare crime scene evidence

Biology: blood, body fluids, hairs and fibers, entomology

Pathology, psychology, odontology, any many more!

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CORPUS DELICTI“Body of the Crime”

You must prove: that a crime occurred that the person charged with the crime was responsible for the crime

Top Reasons for Committing a Crime Money Revenge Sex Emotion--love, hate, anger

Source of Evidence Body Primary and/or Secondary Crime Scene Suspect(s)

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4 Major FEDERAL Crime Labs:

FBIDrug Enforcement Administration (DEA)Bureau of Alcohol, Tobacco, Firearms and

Explosives (ATF)US Postal Inspection Service

Most states also have their own, smaller crime labs

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General Crime Lab Servicesand the materials each unit analyzes

Physical Science Unit: drugs, glass, paint, explosives, etc

Biology Unit: blood and other bodily fluids Firearms Unit: ballistics, comparisons Document Examination Unit: handwriting,

typewriting, questioned documents (ransom notes, etc) Photography Unit: record all phyhsical evidence. Toxicology Unit: presence/absence of drugs Latent Fingerprint Unit: fingerprints Pathology Unit-

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Forensic Pathology

Investigation of sudden unnatural, unexplained or violent deaths

Answer the questions:Who is the victim?What are the injuries, when did they occur, and how

were they produced?5 manners of death: natural, homicide, suicide,

accident, undetermined GO TO SLIDE 25…..

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Crime Scene Team

A group of professionals investigators, each trained in a variety of special disciplines.

Team Members First Police Officer on the scene Medics (if necessary) Investigator(s) Medical Examiner (if necessary) Photographer and/or Field Evidence Technician Lab Experts

pathologist serologistDNA expert toxicologistforensic odontologist forensic anthropologistforensic psychologist forensic entomologistfirearm examiner bomb and arson expertdocument and handwriting experts fingerprint expert

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INVESTIGATORS

“The wise forensic investigator will always remember that he must bring all of his life experiences and logic to find the truth. This means common sense, informed intuition, and the courage to see things as they are. Then he must speak honestly about what it adds up to.”

Dr. Henry LeeChief Emeritus for Scientific Services and the former Commissioner of Public Safety for

the state of Connecticut

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First Officerat the Scene

A Assess the crime scene

D Detain the witness

A Arrest the perpetrator

P Protect the crime scene

T Take notes

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Eye Witness

“Perception is reality.”

As a result an eye witness may not be the best source of crime scene information.

A police composite may be developed from the witness testimony by a computer program or forensic artist.

Faces Composite Programby InterQuest

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Crime SceneSearch Patterns

Spiral Grid

TWO of FOUR PATTERNS

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Crime SceneSearch Patterns

Strip or Line Quadrant or Zone

TWO of FOUR PATTERNS

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Crime SceneSketch

Date: August 14, 2001 Criminalist: Ann WilsonTime: 11:35 Location: 4358 Rockledge Dr

St. Louis, Mo.

A. Couch/sofa

B. Female body

C. Knife

D. Over turned Lamp

E. Chairs

F. Table

G. Fireplace

cD

E

EE

E

E

A G

F

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Crime Scene Mapping(outdoors)

Azimuth--uses a compass beam to determine the location of each piece of evidence

Triangulation--uses two points at the crime scene to map each piece of evidence

Coordinate or grid--divides the crime scene into squares for mapping.

Suspended Polar Coordinate--for use in mapping evidence in a hole

Baseline--set a north/south line and measures each piece of evidence from this line.

AZIMUTHDetermines:

•Direction•Distance•Elevation

TRIANGULATION

Measure from A to B and then to the evidence in a triangular shape.

Coordinate or Grid Mapping

Set a north/south line from a datum point established by a GPS. Make it a perfect square (4 x

4) by shooting the hypotenuse and setting in stakes every foot or meter.

Measure and map the location of each piece of evidence. Then collect evidence and place in containers by grid.

Baseline Mapping

Set a north/south line from the furthest most points of the crime scene. Then measure each piece of evidence from that baseline. Evidence will need a numerical measurement where the piece begins, ends and in the middle.

Evidence Baseline

Suspended Polar Coordinate

Measure and map each layer of evidence as you move down the hole. Use the compass readings from the top to measure degrees and a tank dipping line to measure depth.

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MAPPING TECHNOLOGY

The latest technology includes this Nikon Tsunami with computer. The exact location of all crime evidence can be determined and directly loaded into a computer to produce a crime scene map. Cost = $35,000 for the set.

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Physical EvidenceTransient Evidence--temporary;

easily changed or lost; usually observed by the first officer at the scene

Odor--putrefaction, perfume, gasoline, urine, burning, explosives, cigarette or cigar smoke

Temperature--of room, car hood, coffee, water in a bathtub; cadaver

Imprints and indentations--footprints; teeth marks in perishable foods; tire marks on certain surfaces

Markings

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Physical Evidence (cont)

Pattern or Transfer Evidence--produced by direct contact between a person and an object or between two objects. There are several ways (at least 7) of classifying evidence. In this class, we will use:BiologicalChemicalPhysicalMiscellaneous

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Biological Evidence

Blood Semen Saliva Sweat/Tears Hair Bone

Tissues Urine Feces Animal Material Insects Bacterial/Fungal

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Chemical Evidence

Fibers Glass Soil Gunpowder Metal Mineral Narcotics Drugs

Paper Ink Cosmetics Paint Plastic Lubricants Fertilizer

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Physical (impression)

Fingerprints Footprints Shoe prints Handwriting Firearms

Printing Number restoration Tire marks Tool marks Typewriting

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Miscellaneous

Laundry marks Voice analysis Polygraph

Photography Stress evaluation Pyscholinguistic analysis Vehicle identification

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Physical Evidence (cont)

Conditional Evidence--produced by a specific event or action; important in crime scene reconstruction and in determining the set of circumstances within a particular event.Light--headlight; lighting

conditionsSmoke--color, direction of travel,

density, odorFire--color and direction of the

flames, speed of spread, temperature and condition of fire

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Conditional Evidence (cont.)

Location--of injuries or wounds; of bloodstains; of the victims vehicle;of weapons or cartridge cases; of broken glass, etc.

Vehicles--doors locked or unlocked, windows opened or closed; radio off or on (station); odometer mileage

Body--position; types of wounds; rigor, livor and algor mortis

Scene--condition of furniture, doors and windows; any disturbance or signs of a struggle.

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Evidence Characteristics

Class--common to a group of objects or persons

Individual--can be identified with a particular person or source.

ABO Blood Typing Blood DNA Typing

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Medical Examiner vs the Coroner

A medical examiner is a medical doctor, usually a pathologist and is appointed by the governing body of the area. There are 7 medical examiners in the state of Missouri and 400 forensic pathologists throughout the U.S.

A coroner is an elected official who usually has no special medical training. In four states the coroner is a medical doctor.

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Medical Examiner’sResponsibilities

Identify the deceased Establish the time and date of death Determine a medical cause of death--the injury or disease that resulted in

the person dying

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

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THE BODYRigor Mortis

Temperature Stiffness Time Since of body of body Death

•Warm

•Warm

•Cold

•Cold

•Not stiff

•Stiff

•Stiff

•Not stiff

•Not dead more than 3 hrs

•Dead between 3 and 8 hrs

•Dead 8 to 36 hours

•Dead more than 36 hours

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THE BODYLivor Mortis

Livor mortis is the settling of the blood, causing the skin to change colors.

Lividity indicates the position of the body after death. When lividity becomes fixed, then the distribution of the lividity pattern will not change even if the body’s position is altered.

Lividity usually becomes fixed between 10 and 15 hours after death.

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THE BODYAlgor Mortis

Algor mortis is body temperature.

Average human body temperature: 98.6 F (37 C)

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Time Frame of Death

Condition Appearance Periphery blood drying 30 min to 2 hrs Blue-green discoloration of skin

Right and left area of abdomen 24 hours Entire abdomen 36 hours

Bloating 36 to 48 hours Skin slippage 4 to7 days Absence of smell from bones more than 1 year

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Time Frame of DeathEyeball Changes

Condition Appearance Cornea drying (eyes open) minutes Cornea drying (eyes closed) 2 hours Corneal cloudiness (eyes open) less than 2 hours Corneal cloudiness (eyes closed) 12 to 24 hours Eyeball collapse more than 24 hrs

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One can die of a massive hemorrhage (the mechanism of death) due to a fall (cause of death) as a result of being pushed (homicide), jumping (suicide), falling (accident), or not being able to tell which (undetermined). All of which are manners of death.

THEREFORE,

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CRIME

+ =

What Happened?

Why Did ItHappened?

Who DidIt?

Crime Scene Evidence Collection Witness, Suspect and Motive Development

Post Scene Evidence Processing Cause, manner, time of death

Investigative Stage Profiling

Means Motive Opportunity

Identificationand Arrest of

Suspect

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Forensic Investigations

Include some or all of these seven major activitiesRecognition--ability to distinguish important

evidence from unrelated materialPattern recognitionPhysical property observationInformation analysisField-testing

Preservation--collection and proper preservation of evidence

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Investigations (cont) Identification--use of scientific testing

Physical propertiesChemical propertiesMorphological (structural) propertiesBiological properties Immunological properties

Comparison--class characteristics are measured against those of know standards or controls; If all measurements are equal, then the two samples are considered to have come from the same source or origin.

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Investigations (cont.)

Individualization--demonstrating that the sample is unique, even among members of the same class.

Interpretation--gives meaning to all the information Reconstruction--reconstructs the case events

Inductive and deductive logicStatistical dataPattern analysisResults of laboratory analysis

Lee, Dr. Henry. Famous Crimes. Southington:Strong Books, 2001

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Just A Thought

It’s not what you know that hurts you, its what you think you know and it’s not so . . . . .Mark Twain

How does this apply to forensic science and crime investigations?