Forensic Science Notes

Introduction to Forensics

  • Forensic: Pertaining to, connected with, or used in courts of law.
  • Scientist: One engaging in a systematic activity to acquire knowledge.
  • Forensic Science: Application of a broad spectrum of sciences and technologies to investigate and establish facts of interest in relation to criminal or civil law.

Requirements of the Forensic Scientist

  • No specific content on this page.

Staffing Issues

  • Forensics: A general term which may be applied to a number of disciplines, such as anthropology or odontology.
  • Criminalistics: Applies the application of chemistry, biology, or physics to evidence analysis and addresses crime scene investigation and reconstruction.

Accreditation and Certification

  • Lists various accreditation and certification bodies:
    • CRIME LABORATORY ACCREDITATION BOARD
    • AMERICAN SOCIETY OF LABORATORY DIRECTORS
    • AMERICAN ACADEMY OF FORENSIC SCIENCES
    • NORTH AMERICAN FORENSIC ENTOMOLOGY ASSOCIATION (NAFEA)
    • AMERICAN BOARD OF CRIMINALISTICS

Qualifications of a Forensic Examiner

  • On-the-job training assists entry-level criminalists in gaining necessary skills and knowledge for career development.
  • Requirements to be a forensic examiner:
    • Possess a baccalaureate degree in natural science: emphasis in physics, biology, chemistry, or forensic science.
    • DNA technical managers must have a Master’s Degree.

Defining a Crime Scene

  • Location of criminal activity.
  • Size of area.
  • Type of crime committed.
  • Physical location of crime.

Location of Criminal Activity

  • Primary Crime Scene: Where the original crime occurred.
  • Secondary Crime Scene: Subsequent crime scenes.
  • Example given: Walter White / Krazy 8 scenario illustrates primary and secondary crime scenes.

Size of Crime Scene

  • Macroscopic: One location, composed of many microscopic crime scenes.
  • Microscopic: Focuses on specific types of physical evidence.
  • Example given: Walter White / Krazy 8 scenario illustrates macroscopic crime scenes.

Type and Physical Location

  • Type of crime committed: Homicide, robbery, sexual assault, etc.
  • Physical location of crime scene: Indoors, outdoors, vehicle, etc.
  • Organization: Organized vs. disorganized.

Crime Scene Investigation

  • Key processes: Recognition, Identification, Individualization, Reconstruction.

Crime Scene Investigation Goals

  • What happened?
  • Where did it happen?
  • When did it happen?
  • Why did it happen?
  • Who may have perpetrated these actions?
  • How was the incident carried out?

Processing a Crime Scene

  • 8 universal rules:
    • Safety first
    • Secure and protect the scene
    • Fulfill the basic legal requirements
    • Survey/photograph the scene
    • Identify and mark evidence
    • Collect, label, and package evidence
    • Diagram the scene
    • Write a report

Crime Scene Safety

  • Guidelines exist to protect investigators at crime scenes.
  • Must wear latex gloves and shoe covers.
  • Must wear masks when potentially infectious dust or mist is at the crime scene.
  • Must be alert to sharp objects.
  • Must maintain red biohazard bag for disposal of contaminated materials.
  • Must take notes without gloves.
  • Must not eat, smoke, or drink at the crime scene.
  • Must launder any clothing that may be contaminated.

Search Methods for Evidence

  • Spiral search method
  • Grid method
  • Strip or line search
  • Quadrant or zone search

Search for Evidence

  • Evidence must also be collected from the decedent (body).
  • Role of Forensic Pathologist.
  • Role of Pathology assistant or CSI.

Photography at a Crime Scene

  • Elements of a camera and photography concepts

  • Shutter Speed: Measured in seconds, controls the duration of light exposure. Faster shutter speeds freeze action, while slower speeds allow for movement blur.

    • 1/10001/1000 (freeze action)
    • 1/601/60 (hand hold)

  • Aperture (f-stop): Controls the amount of light entering the lens. Smaller f-numbers (e.g., f/1.4) indicate larger lens openings and more light, while larger f-numbers (e.g., f/32) indicate smaller openings and less light.

  • ISO: Indicates the film or sensor's sensitivity to light. Low ISO (e.g., 100) is for less light and high ISO (e.g., 6400) for more light

  • Exposure Time: 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1

  • Focal length: distance between lens and image sensor

Photography: Examples of Settings

  • ISO = 100, Shutter = 1/601/60, f/8
  • ISO = 100, Shutter = 1/1251/125, f/5.6
  • ISO = 100, Shutter = 1/601/60, f/5.6
  • ISO = 100, Shutter = 1/601/60, f/16

Reflectance

  • Examples:
    • Reflect 90%
    • Reflect 50%
    • Absorb all light

Crime Scene Photos Documentation

  • Includes:
    • Date
    • Time
    • Agency
    • Case #
    • Photographed by

Types of photos

  • Establishing Shot
  • Entry
  • Scene
    • LAZER DR808399
    • 9-23-50PB

Evidence Photos

  • Includes:
    • Length
    • Location
    • Point of Convergence
    • Approx Angle
    • Pad by:
    • North Up
    • 90 degrees, perpendicular

Photo Log Sheet

  • Includes:
    • Agency
    • Case Number
    • Incident
    • Victim
    • Date/Time of report
    • Subject
    • Location photos taken
    • Photographer
    • Assisted by
    • Film
    • Notes

Crime Scene Photos: Vehicle/Traffic Accident

  • Driver’s viewpoint
  • Point of impact
  • Traffic control devices
  • Skid marks
  • Roadway condition and environment
  • Obstructions
  • Biological evidence
  • Tire track location
  • Footprints
  • Impression prints
  • Trace
  • Defects
  • Debris
  • Roadside environment
  • Interior of vehicle
  • Establishing shots (VIN, plates, overview)

Crime Scene Photos: Death Investigation

  • Establishing photos of exterior
  • Perspective
  • Rooms with activity
  • Areas without activity
  • Establishing, midrange, close-up
  • Impression evidence
  • Establishing of body
  • Midrange of body
  • Close-up of body
  • Weapons
  • Markers of body

Crime Scene Photos: Arson

  • Establishing photos of exterior
  • Sides
  • Flashover
  • Flame color
  • Crowd
  • Individuals
  • Exterior shots
  • Establishing interior
  • Midrange interior
  • Immediate surroundings of evidence
  • Close-up interior
  • Actively Burning Scene / Non -Burning Scene

Image Enhancement

  • Must ensure the image is not "changed!"
  • Following guidelines by the Scientific Working Group on Imaging Technology (SWGIT).
  • Maintain a master copy.
  • Keep an enhancement log.

Videographer Requirements

  • Understand basic elements of forensic videography
  • CSI experience
  • Video experience

The Crime Scene Video

  • Initial walk through
  • Map the layout
  • Secondary walk through
  • Team leader consultation

Techniques for Crime Scene Video

  • Slow Pan: 8-10 seconds per quarter turn.
  • Capture evidence from several angles.
  • Include establishing shots.
  • Zoom in/out on objects.

Crime Scene Sketches

  • Examples of rough and finished sketches.

Requirements for Crime Scene Sketches

  • Title or caption
  • Legend of abbreviations
  • Symbols
  • Numbers of letters used
  • Compass designation
  • Scale, if drawn to scale
  • Documentation block with case number, offense type, victim’s names, location, date and time, and sketcher’s name

Sketch Example

  • Additional example sketch

Crime Scene Notes

  • Date & time
  • Arrival info
  • Scene description
  • Evidence info: who discovered, time, location, packaging, current location
  • Victim description
  • CSI team members

Collecting and Packaging Evidence

  • Use separate containers.
  • Use plastic bottles, manila envelopes, paper bags.
  • Air dry evidence before packaging.
  • Include evidence identification labels.

Chain of Custody

  • Is a list of all persons who come in possession of an item of evidence.
  • A custody record and analysis request form is used.

Reference Samples

  • Collection of reference samples

Introduction to Physical Evidence

  • Roles of Physical Evidence:
    1. Reconstruct the Crime Scene & Sequence of Events.
    2. Determine whether or not a crime occurred.
    3. Link an individual with another or with a crime scene.
    4. Provide Investigative Leads to Investigators.
    5. Provide facts to a jury which may assist in the determination of the guilt or innocence of an accused.
    6. Provide evidence to link serial homicide or rape case.

Advantages of Physical Evidence

  • Provides a tangible object for the jury to see.
  • Can be taken into the jury room.
  • The defendant cannot distort the physical evidence.
  • Some cases cannot be solved without the physical evidence.
  • Physical evidence is not subject to memory loss.
  • The defendant can have the evidence tested by an independent expert.

Types of Evidence

  • Anything
  • Materials collected and scientifically analyzed to determine the nature and circumstances of a crime.
  • Direct: Establishes a fact (eyewitness).
  • Circumstantial: Provides an inference about what happened (more reliable than direct).

Evidence Analysis

  • Identification:
    • Determine the physical or chemical identity of a substance.
    • Answer the question: “What is it?”
  • Comparison:
    • Suspect and standard specimens.
    • Answer the question: “Does it Match?”

Physical Evidence Characteristics

  • Class Characteristics
    • Intentional or recurring characteristics
    • Evidence associated with one group
  • Individual Characteristics
    • Unintentional, random, and unique features
    • Evidence associated with a common source with a high degree of probability

Fingerprints & handwriting

  • Examples of fingerprints & handwriting

Probability

  • The frequency of occurrence of an event.
  • In all cases, it is not possible to state with mathematical exactness the probability that the specimens are of common origin.
  • It can only be concluded that this probability is so high as to defy mathematical calculations or human comprehension.

Class Evidence

  • Inability to assign exact or even approximate probability values to the comparison of most class physical evidence.
  • Currently trying to update statistical databases for class evidence.
  • Value of class evidence:
    • Corroboration
    • Additive probability

From Class to Individual Evidence: Key Questions

  • How many striations are necessary to individualize a mark to a single tool and no other?
  • How many color layers individualize a paint chip to a single car?
  • How many ridge characteristics individualize a fingerprint?
  • How many handwriting characteristics tie a person to a signature?

Forensic Databases

  • The Integrated Automated Fingerprint Identification System (IAFIS)
  • The Combined DNA Index System (CODIS)
  • The National Integrated Ballistics Information Network (NIBIN)
  • The International Forensic Automotive Paint Data Query (PDQ) database
  • SICAR (shoeprint image capture and retrieval) is a shoeprint database.

Seven Types of Evidence

  • Trace evidence
  • Indented or impression evidence
  • Chemical evidence
  • Biological Evidence
  • Fingerprint evidence
  • Firearm and tool mark evidence
  • Questioned document evidence

Identifying Physical Evidence

  • Presumptive Tests
    • Identify suspect evidence (class)
    • Cheaper
    • Faster
    • Can be done at crime scene
    • Less training needed
    • Help focus investigation
  • Specific/Confirmatory Tests
    • Can lead to individual classifications
    • Costly
    • Time consuming
    • Typically done in the lab
    • More exact procedure
    • Match a suspect to a crime

Strengthening Forensic Science in the U.S.

  • Report of 2006-2009 study on forensic science
  • Assess present and future resource needs
  • Recommendations for maximizing forensic technologies
  • I.D. potential scientific advances
  • Recommend programs to increase the number of scientists
  • Disseminate best practices and guidelines
  • Examine AFIS
  • Additional issues
  • 2009 issued report

Challenges Facing Forensic Science

  • Standardized terminology and reporting
  • Lack of rigorous research
  • Mitigation of personal bias
  • Accreditation and certification
  • Quality control
  • Code of ethics
  • Insufficient education/training

Forensic Scientist Ethics

  • Obligation to the truth
  • Present facts without distortion
  • Witness’s expertise allows them to properly present evidence
  • Avoid overly definitive or inconclusive statements

Forensic Evidence

  • Forensic evidence: evidence generated through science
  • Circumstantial
  • Useful for:
    • Leads
    • Suspect elimination
    • Corpus delicti
    • Corroboration of confession
    • Links
    • Proving essential elements
    • Alibi
    • Establishing innocence
    • Encouraging confession
    • Reasonable suspicion/probable cause
    • Strong Cases

Forensic Evidence

  • Evidence
  • Left at crime scene
  • Collected by investigators
  • Tested and produces results
  • Allowed into court according to rules of evidence

Admissibility of Evidence

  • Three major tests:
    • Frye test (1923):
      • Is the scientific theory generally accepted in the scientific community?
      • Is the scientific method used generally accepted in the scientific community?
      • Has the technique been applied correctly?
    • Federal Rules of Evidence Rule 702 (1975)
      • Judge is the gatekeeper
    • Daubert test (1993):
      • Has the scientific theory or technique been tested?
      • Has the scientific theory or technique been subjected to peer review and publication?
      • What are the known or potential error rates of the theory or technique when applied?
      • Do standards and controls exist and are they maintained?
      • Has the theory or technique been generally accepted in the relevant scientific community?

Admissibility of Evidence (cont.)

  • Revised Rule 702:
    • Is it good science?
    • Does it incorporate reliable data?
    • Is the data applied by a qualified expert?

Is it good science?

  • Scientific vs. technical evidence
    • Scientific: Knowledge generated through the scientific method
    • Subjecting testable hypotheses to experiment in an effort to disprove them
    • An opinion that defies testing is not scientific
  • The Scientific Method
    1. Observation
    2. Question
    3. Hypothesis
    4. Experiment
    5. Analysis and conclusion

Does it incorporate reliable data?

  • Most controversial area
  • Data must be shown accurate
  • Data collection accuracy
  • Data records
  • Data analysis

Is data applied by qualified expert?

  • Depends on educational and experiential background
  • Each field is different

Potential Problems

  • Rule 403 (balancing test for admissibility of evidence)

Choosing the Expert

  • Legal standard
  • Effective experts:
    • Able to teach
    • Perceived as reliable
    • Track record
    • Image

Opposing Evidence

  • Procedures
  • Areas of vulnerability
  • Rule 403
  • Credentials