Crime Scene Investigation

Defining a Crime Scene

“Any place where a crime scene has been committed.”

Many different ways to classify a crime scene:

1. Location of original criminal activity
   • Primary scene: site of the original criminal activity
   • Secondary crime scenes: any subsequent locations
   • This classification scheme has nothing to to do with a scene’s relative importance (simply a sequence of locations)
2. Size of the crime scene
   • Macroscopic refers to the overall crime scene
   • Microscopic refers to the trace evidence (smaller scenes within the larger)
3. Other
   • No single definition works for all crime scenes
   • The crime scene expands and changes as the evidence dictates the:
     • Type of crime committed
     • Crime scene condition
     • Physical location of the crime
     • Type of criminal behaviour associated with the scene

The Importance of Physical Evidence

Three major avenues availble to investigators to solve crimes and are very helpful with reconstructing a crime scene which are:

• Confessions
• Eyewitness accounts
• Physical evidence (only physical evidence is free of inherent error or bias)

Physical evidence can:

• Prove a crime was committed
• Link a system with a victim or with a crime scene
• Establish identity of persons associated with the crime scene
• Corroborate or refute testimony
• Be more reliable than testimony
• Provide investigative leads
• Identify unknown substances

Physical evidence often lacks individual characteristics that can tie a suspect conclusively to a crime. The likelihood that the suspect and victim are related depends on the number of pieces of evidence linking them and the uniqueness of the evidence. Principles of crime scene investigation are critical, helping: recognize, preserve, collect, and interpret physical evidence.

The Product Rule and Probability

The product rules states that the probability of two independent events occurring together can be calculated by multiplying the individual probabilities of each event occurring alone

General Crime Scene Procedures

Scene Management

Crime scenes are busy places and proper management of a scene is critical. The lead investigator is often the most experienced individual and is responsible for managing:

• Information
• Personnel
• Technology
• Logistics

Several different management models are available based on the allocation of personnel, resources, training, expertise, etc. Maintaining good communication among all personnel is critical to a successful resolution to the investigation

First Responding Officer

The first responder is the first person at the scene of a crime. They are the only people to view a crime scene in its most original and pristine condition. Their actions ar the scene can have far reaching consequences. They should always keep in mind that they are the first step in linking a victim to a suspect. The first responder has several important duties.

The Duties of a First Responder

1. Assist the victim and prevent any changes to the victim
2. Search for and arrest the suspect if they are still there
3. Detain any witnesses
   • Keep them seperated to maintain objectivity
   • Do not let them go back to the crime scene
4. Protect and secure the crime scene:
   • Establish a perimeter
   • Prevent contamination
   • Limit access to the scene
5. Document all movements, alterations, or changes made to the crime scene and pass the information along

Crime Scene Survey

The preliminary scene survey is the first examination or orientation of the crime scene by the crime scene investigator. The following guidelines should be followed:

• Use the walk-through as a mental beginning for a reconstruction theory - be prepared to change your mind
• Note any evidence that needs immediate protection or processing
• Be aware of impending weather conditions that could affect a scene
• Note possible points of entry or exit
• Briefly record initial thoughts on who, what, where, when, and how
• Assess the scene to determine what kind of personnel, equipment, etc. will be required
• Notify superior officers as needed
• Transient vs condition FOLLOW UP!!!

Crime Scene Documentation and Forensic Photography

The single most important task of the crime scene investigator is generating a permanent record of the scene and its physical evidence as it was before processing. This is the most time-consuming activity at the scene and requires a systematic and organized approach. It may not be evident what is truly important, so everything must be documented.

Four Major Documentation Tasks

1. Notetaking
   • Effective notes serve as an important written record
   • General guideline for taking notes is to consider who, what when, where and why

   • Good Note Factors	Information Collected
     Notification Information	Date, Time, Method of notification
     Arrival Information	Date, Time, Hwo, Means of transportation
     Scene Description	Weather, Location, Condition, Major structures, Transient or conditional evidence?
     Victim Description	Position, Wounds, Clothing, Jewelery, Only move a body with the permission of a medical examiner
     Crime Scene Team	Who is assigned where, Start / end time

2. Videography
   • Has now become a routine procedure
   • Can provide virtual image of the scene
   • The form of documentation
     • Should be performed after the crime scene survey
     • Should not include any members of the investigation team or their equipment
     • Should not be narrated or include an audio recording of subjective information at the scene
     • Can provide a valuable tool for overall, accurate impression of the crime scene, but is no substitute for any other tasks
3. Photography
   • Photography provides a true and accurate pictoral record of the crime scene and the physical evidence present
   • Normally performed immediately after videography or after preliminary scene search
   • The number of photographs vary from scene to scene
     • Too many is better than too few
   • Every crime scene photograph must be recorded in a photo log
     • Includes the time taken, camera settings used, distance to object, type of photograph taken, brief description of image
4. Sketching
   • The final documentation task
   • Must obtain and record accurate measurements of the scene
   • All previous tasks do not have any information about the objects actual size* or **measurement of scene and its physical evidence
   • Provides proper perspective of the scene and how the physical evidence relates to the scene
   • Two main types:
     • Rough sketch
     • Final sketch

Crime Scene Searches

The preliminary crime scene search is simply for orientation purposes and preservation of transient evidence. After careful documentation is complete (but before evidence collection starts) a more thorough search for previously overlooked items is performed. Crime scene search patterns vary in style but share the same goal of giving a search organization and structure.

There different types of searches and ultimately, the specific search pattern used is unimportant as along as the method is methodical and systematic.

Search Methods

Several typical examples of crime-scene search patterns. The pattern selected normally depends on the size and locale of the scene and the number of collectors participating in the search.

1. Spiral
   • Begin in the middle of an area and follow a clockwise pattern outward
   • Advantages: very effective for small interior scene searches
   • Disadvantages: potential to miss evidence increases and the perimeter increases
2. Strip
   • A group of investigators begin at one end of the search area and they walk down that strip, at arm’s length in a linear fashion
   • Advantages: Used for large outdoor crime scene
   • Disadvantages: Area search only once, so evidence can be missed
3. Grid
   • Searchers begin at one end of the search area and proceed in a line to the end of the search area. Once completed, searchers cover the same area from a 90° angle
   • Advantages: a second pair of eyes is searching
   • Disadvantages: takes longer than other methods
4. Zone
   • The search area is broken down into zones and each zone is searched individually
   • Advantages: useful in small confined areas
   • Disadvantages: may vary depending on individual search methods used within each zone
5. Ray
   • Searchers start at common / central point and walk away from each other
   • Advantages: good for very large outdoor areas
   • Disadvantages: not ofen used, ineffective

Collection and Preservation of Physical Evidence

Collection and preservation of physical evidence is extremely important to an investigation. Evidence must be collected, packaged, marked, sealed, and preserved in a consistent manner. Different types of physical evidence will require different packing and collection techniques, Transient, fragile or easily lost evidence is given priority.

To secure trace evidence most items are packaged twice in a primary and secondary container. The outer containers are then completely sealed with tamper resistant tape and marked with information about the item (date and time, when the item was collected, location where the item was found). A seal is palced over the opening and initial by the collector.

Some types of evidence (liquids, volatiles, biological evidence) requires special packaging considerations.

• Airtight, unbreakable containers
• Allowed to air dry before packaging

Each item of evidence is packaged separately to avoid cross-contamination and it is the job of the collector to ensure this is done properly.

The Chain of Custody

• A list of all people who came into possession of an item of evidence
• An unbroken chain of custody must be established to get a piece of evidence presented in a court of law

Crime Scene Reconstruction