Introduction to Forensics Crime Investigation

Introduction to Forensics

• Direct evidence establishes facts through eyewitness testimony or confessions.
• Circumstantial evidence needs interpretation, and frequently involves DNA.
• Locard's exchange principle states that "every contact leaves a trace."
• Eyewitness testimony is limited by intentional and change blindness.
• Forensic science investigates a crime (whether it was committed), determines responsibility, and whether a prosecution is justified.

Crime Scenes

• Crime scene is location of illegal act, where evidence is collected.
• Primary crime scene is where the actual crime took place, and secondary scenes are related locations.
• Crime scenes are processed by trained personnel, including crime scene investigators (CSIs).
• Safety procedures are crucial to preserve evidence.

Role of Investigators

• Investigation process involves reporting a crime, evidence preservation and recovery, analysis, conclusions, and prosecuting the case.
• Crime scene examination involves preservation, recording, documenting scene, identifying evidence, and gathering items
• CSI role: confirms committed crime, preserves scene, identifies key evidence, documents all evidence and prepares court statements.

Types of Crime and Initial Tasks

• Volume crimes involve lesser offenses such as burglary, theft of property. Initial tasks for these involve preserving life, protecting property, maintenance of order, preserving evidence, and apprehending offenders.
• Major crimes involve more serious offenses such as murder, manslaughter, rape, arson, or terrorism. Initial tasks involve preserving life, protecting property, maintenance of order, preserving evidence, and apprehending offenders.

Health and Safety

• Set up safety procedures (cordons and rendezvous points) to prevent people from accessing the crime scene.
• Identify hazards in the crime environment, such as biological and chemical hazards.
• Establish safety distances between people and the crime scene.

Evidence Packaging and Preservation.

• Correct packaging, minimizing handling and inappropriate storage.
• Ensure proper packaging, including storage and handling (tools, gloves, PPE).
• Prevent cross-contamination during the packaging and storage process.
• Preserve evidence integrity by preventing contamination, damage, or degradation.
• Proper labeling and record keeping necessary to maintain chain of custody and preserve integrity.

Crime Scene Management and Searches

• Use of zoning and search techniques to systematically search.
• Physical zones to systematically manage the crime scene.
• Techniques like strip/parallel search pattern, grid method, and outward/inward spiral.

Documentation and Photography

• Detailed crime scene sketches with measurements to detail the scene (e.g., dimensions of the scene, locations of objects).
• Photographs (long range, medium range, close-up views, with a 'three-shot rule') to document the scene before, during and after critical evidence collection.
• Photography must follow established procedures, with considerations for scale, quality, and resolution.

Forensic Examinations- Special Focus on Documents, Fraud, and Forgery

• A document (official or not) can be analyzed for its authenticity given its characteristics, author(s), alterations, additions, erasures and/or obliterations, and the method of creating the document
• Documents can be analyzed to identify the author and method (printing type, handwriting) and any tampering or alterations.
• Important to consider ink analysis and paper analysis, as well as special properties(watermarks, fluorescence markers or obliterations)
• Using analytical methods in comparison with related docs (e.g. handwriting) can aid in determining the source of a document or authenticity.

Fingerprint Analysis

• Fingerprints unique to each individual and remain consistent throughout their whole life.
• Fingerprint patterns used to identify individuals in crime scenes.
• Fingerprints are collected under controlled conditions and documented for comparison.
• Classification systems used to sort and match fingerprints (Henry system using patterns and ridge characteristics).
• Types of fingerprints include arches, loops and whorls.
• Fingerprint analysis used to identify individuals.

Trace Evidence

• Trace evidence are the marks left from contacts between hands and surfaces, providing evidence for investigations.
• Using forensic science to identify an individual for forensic cases
• Chemical composition can change, depending on the surface and time factors.

Evidence Recovery

• The physical examination of exhibits and the retrieval of any evidence are crucial.
• When receiving exhibits, carefully examine and document the packaging for signs of tampering or damage.
• Cut or remove packaging appropriately (e.g., cutting a new hole in the packaging).
• Properly handle and package any debris/fragments fallen from items being analyzed..
• Photograph and document anything unusual that can be utilized as part of a thorough forensic investigation
• Properly record all recovered evidence (e.g., label and seal).

Documenting Scenes and Evidence

• Crime scene reports/logs/photographs (date, time, location) which details scene parameters.
• Reports include observations of local conditions (weather, lighting) and photographs, and documentation of everything important to the crime.
• Photographs that document the entire scene and all objects found.
• The information obtained from the crime scene must be documented in detail and prepared contemporaneously for court use

Personal Protective Equipment

• PPE is used to maintain safety of personnel and maintain the integrity of evidence.
• PPE such as face masks, gloves, appropriate eyewear, and specialist clothing.