Chapter 5: Crime Scene Reconstruction

Overview

Instructor: O'Neil
Focus: Crime Scene/Forensic Science Technology

Objectives of Crime Scene Reconstruction

Understand key individuals associated with the process of reconstruction.
Explore bloodstain pattern analysis.
Examine forensic techniques used in reconstruction of crime and accident scenes.

What is Crime Scene Reconstruction?

Defined as "advanced crime scene investigation."
Involves using collected evidence to:
- Determine how the crime was committed, detailing the sequence of actions and methods used.
- Establish the factual sequence of events, from the initial moments to the aftermath.
- Discern what logically could have or could not have happened during the crime's commission, based on scientific principles and evidence.
The process entails:
- Interpreting all available evidence from various forensic disciplines (e.g., ballistics, toxicology, trace evidence, DNA).
- Logically constructing a plausible scenario of the crime that is consistent with all physical evidence.
- Practitioners must possess:
  - Deep knowledge of scientific principles and forensic methodologies.
  - Strong logical reasoning skills to connect disparate pieces of evidence.
  - An open mind to revise hypotheses based on new evidence or contradictory findings, demonstrating an iterative approach to investigation.

Individuals Who Practiced Crime Scene Reconstruction

Edmond Locard (1877–1966)
- Renowned French forensic scientist, pioneer of forensic science.
- Developed Locard’s Exchange Principle: "Every contact leaves a trace." This fundamental principle states that whenever two objects come into contact, there is a transfer of material between them, forming the basis for trace evidence analysis.
Hans Gross (1847–1915)
- Influential Austrian criminal expert and examining magistrate.
- Known as the Father of Criminal Investigations for his insistence on the scientific method in criminal investigations.
- Instrumental in the creation of the field of criminalistics through his comprehensive manual for magistrates; included fields like crime scene photography and documentation.
Edward Oscar Heinrich (1881–1953)
- American forensic scientist, often referred to as America's Sherlock Holmes.
- Expert in integrating chemistry, microscopy, spectrography, and other analytical techniques with criminal investigations.
- His methodologies led to the resolution of many notable cases by piecing together seemingly insignificant details.

Process of Crime Scene Reconstruction

Begins with the arrival at the scene and performing an initial walk-through.
- This involves securing the scene, documenting initial observations with photographs and sketches, and identifying potential evidence. The goal is to develop a rough idea of what may have occurred.
- Formulate an initial hypothesis which may change as new information emerges, allowing for iterative refinement.
Critical aspects include:
- The systematic development of a comprehensive theory regarding how the crime occurred, supported by evidence.
- Crime scene reconstruction is considered the final and synthesizing step of the investigative process, drawing upon all previous findings.
Essential requirements:
- Collaboration with all involved individuals, including law enforcement, forensic scientists, medical examiners, and legal professionals, to ensure a holistic approach.
- Incorporation of new information from various sources to either support the current hypothesis or prompt re-evaluation and revision of theories.
- The reconstruction outlines the detailed sequence of events before, during, and after the crime, considering various timelines.
- All known factors must be considered, including the precise location and actions of individuals involved in the crime, weapons used, and environmental conditions.
Important to highlight that investigators may need to testify about the reconstruction process:
- They must be prepared to defend their conclusions against alternative theories in court.
- Must base conclusions strictly on scientific principles, rigorous logical reasoning, and well-documented personal experience and training.

Bloodstain Pattern Analysis (BPA)

A specialized field requiring extensive training and experience, often performed by certified experts.
Involves interpretation of bloodstains to recreate the mechanism producing the observed bloodstain pattern, providing critical insights into the dynamics of the crime.
Key determinations include:
- Movement and direction of individuals (victim and assailant) during and after the incident.
- Sequence of events leading to the bloodstain formation, establishing the chronology of actions.
- Area of convergence (2D location) and area of origin (3D location) of the bloodstain pattern to identify where the impact occurred.
- Number of impacts that produced the bloodstains, which can suggest the intensity and duration of an assault.
- The type of weapon used (e.g., blunt force, sharp object, firearm) based on the characteristics of the spatter.
Bloodstain analysis can corroborate or contradict witness statements and is critical for guiding further investigation, including DNA analysis and evidence collection strategies.

Examination Techniques in Bloodstain Pattern Analysis

Investigators examine:
- Size, shape, distribution, and location of bloodstains to determine their significance and the force applied. For example, smaller, more numerous stains often indicate higher impact velocity.
- Directionality of bloodstains: The pointed end (tail) of an elongated bloodstain indicates the direction of travel, while the wider, rounded end typically faces the direction of origin.
- Angle of impact, which is crucial for recreating crime scene dynamics and determining the relative positions of objects or individuals when the blood was shed.
Bloodstains are categorized into three basic types:
- Spatter: Blood projecting through the air from a mechanism, further categorized by velocity:
  - Low-velocity impact spatter: Typically large drops (>$4mm), often from passive drops or blunt force with minimal force.
  - Medium-velocity impact spatter: Medium-sized drops ($1mm - 4mm), associated with blunt force trauma, stabbings, or cast-off blood.
  - High-velocity impact spatter: Fine mist-like drops ($<1mm), often resulting from gunshots, explosions, or high-speed machinery.
- Passive Stains: Created by dripping, flowing, or pooling of blood under the influence of gravity:
  - Transfer stains: Blood moving from one blood-bearing surface to another non-blood-bearing surface.
  - Drops: Resulting from individual blood drops falling vertically.
  - Flows: Larger volumes of blood moving across a surface.
  - Large-volume stains/pools: Accumulations of blood from significant bleeding.
- Altered Stains: Patterns whose appearance has been changed by environmental or external factors:
  - Clotted: Indicates a time lapse since deposition.
  - Diluted: Suggests contact with water or other liquids.
  - Diffused: Blood spreading into absorbent material.
  - Affected by insects: Patterns created by insect activity (e.g., fly specking).
  - Voids: An absence of blood in an otherwise continuous bloodstain pattern, indicating an object was present during the spatter event and subsequently removed.

Angle of Impact Calculation

The angle of impact can be calculated using the following formula: ext{Angle of impact} = ext{sin}^{-1} igg(rac{ ig( ext{width of stain} ig)}{ ig( ext{length of stain} ig)} igg)
- Where the ratio of the width to the length of an elliptical bloodstain provides an approximation of the impact angle. For example, for a bloodstain with a width of 9mm and a length of 18mm, the calculation would be ext{sin}^{-1} (9/18) = ext{sin}^{-1} (0.5) = 30° angle of impact.

Definitions of Bloodstains

Swipe: A bloodstain resulting from transferring blood from a moving blood-bearing surface onto another surface, often indicating the direction and motion of the moving object or body part.
Wipe: An altered bloodstain pattern caused by an object moving through an existing, wet bloodstain, often distorting the original pattern.
Transfer: A bloodstain created from direct contact between a blood-bearing surface and another surface, leaving an impression of the object's shape or texture.
Parent Stain: The larger, originating bloodstain from which a satellite stain is produced upon impact.
Satellite Stain: Smaller bloodstain(s) that detach from the parent stain due to blood impacting a surface, often found adjacent to the parent drop.
Cast-off: Droplets of blood released from an object (e.g., weapon) due to its motion or sudden stop, creating a linear pattern indicative of the object's trajectory.
Drip Stain: Blood resulting from drops falling due to gravity, typically circular or slightly elliptical depending on the surface and height.
Void: An absence of blood in a continuous bloodstain pattern, indicating the obstruction or removal of an object or person that was present during the bloodshed event.
Expirated Blood: Blood expelled due to airflow from the nose, mouth, or a wound (e.g., from coughing or sneezing), often characterized by air bubbles and a reddish-brown color.

Accident Reconstruction

Involves crime scene investigators and forensic engineers analyzing various scenarios:
- Vehicle fatalities, including complex hit-and-runs, requiring analysis of collision dynamics, occupant kinematics, and vehicle damage.
- Structural failures (e.g., bridge collapses, building fires) and various industrial accidents, examining material science, engineering designs, and environmental factors.
- Vehicle crashes in civil cases, often focusing on liability, speed, and sequence of events.
Key processes include:
- Examining speedometers: Analyzing the final position of the needle or electronic data recorders (EDRs) to assess travel speed at the time of impact.
- Measuring the length of skid marks: Using formulas involving the coefficient of friction and drag factors to determine stopping distances and pre-impact speeds.
- Collecting comprehensive physical evidence from the scene: This includes vehicle debris, tire marks, road conditions, and any impact points.
- Interviewing witnesses: Opting for thorough, unbiased interviews to gather accurate facts and perspectives from different viewpoints.
- Reviewing maintenance records of the vehicle involved: To identify any potential mechanical failures, recalls, or issues that could have contributed to the accident.

Forensic Shooting Reconstruction

Analyzing shooting incidents involves:
- Mastery in trajectory analysis, which determines the path of a projectile from its source to its impact point, considering gravity, air resistance, and intermediate targets.
- Ballistics, which studies the motion of projectiles and their effects:
  - Internal ballistics (what happens inside the firearm).
  - External ballistics (what happens to the bullet in flight).
  - Terminal ballistics (what happens when the bullet hits a target).
- Important considerations include:
  - Type of weapon used: Influences projectile characteristics and energy transfer.
  - Nature and specifications of the ammunition: Affects penetration, wound characteristics, and ricochet potential.
  - Distance to the target: Critically impacts projectile energy and potential for GSR (gunshot residue) deposition.
  - Angles at which bullets entered and exited the surface: Vital for determining the relative positions of the shooter and victim, and identifying ricochet paths.
  - Other factors influencing trajectory outcomes: Such as intermediate impacts (e.g., through glass, clothing) and environmental conditions.
Tools for reconstruction may include:
- Wooden dowels and laser pointers to visually determine angles of impact and projectile paths, helping to create a 3D representation of the incident.

Reconstruction Videos and Case Studies

Notable reconstruction case studies:
- Pistorius Crime reconstruction in court, highlighting challenges in presenting complex forensic data.
- Testimonies from crime scene experts in the Alex Murdaugh murder trial, showcasing the interpretation of multiple evidence types.
- Debates surrounding expert testimony in the Palm Springs quadruple murder retrial, emphasizing the importance of scientific rigor and logical consistency.

Activity and Discussion Points

Critical questions for discussion and understanding:
- True or False: Every forensic investigator is a bloodstain pattern analyst. (False, BPA requires specialized training).
- What significance does a void hold within a bloodstain pattern? (Indicates an object was present and removed).
- How do blood swipe and blood wipe differ? (Swipe is blood transferred from a moving object; wipe is an object moving through existing blood).
- Who is typically called upon for accident reconstruction? (Crime scene investigators and forensic engineers).
- Which individual is credited for combining chemistry with criminal investigations? (Edward Oscar Heinrich).
- Options include Hans Gross, Edward Oscar Heinrich, and Edmond Locard.