Class Detail: Crime Scene Investigation

What is Crime Scene Investigation?

Rationale

Crime Scene Investigation is critical to the criminal justice system. The role of the crime scene investigator is critical in obtaining, photographing, and preserving evidence at a crime scene. An understanding of crime scene investigation is crucial for the forensic scientist to further analyze the crime and suspect.

Objectives

The student will be able to:

1. Work as a productive member of a team.

2. Conduct a systematic search of a mock crime scene.

3. Develop a crime scene sketch.

4. Demonstrate proper techniques of collecting and packaging evidence at a crime scene.

Engage

Show a crime scene clip of your choice (if a video is not available, you can role play a crime scene investigator that does not follow protocol). Have students discuss the procedures that they feel are true to crime scene investigation and those they feel are not true. Use the Discussion Rubric for assessment.

Key Points

I.   Process a Crime Scene

     A. Isolate and secure the scene

     B. Document the scene

     C. Search for the evidence

     D. Collect and package the evidence while maintaining the chain of custody

     E. Submit the evidence for analysis

II.  First Officer on the Scene

     A. A – Assess the crime scene and assist the injured

     B. D – Detain the witness(es)

     C. A – Arrest the perpetrator

     D. P – Protect the crime scene

     E. T – Take notes

III. Secure the Crime Scene

     A. Look for signs of life

     B. Cordon off the scene (only allow authorized personnel in)

     C. Bodies should be certified as “dead” by a medical examiner (ME) before being moved

IV. Survey the Crime Scene

     A. A walk-through is performed by the crime scene investigator, the first officer, and sometimes the lead

         detective

     B. Record initial observations of who, what, where, when, and how

     C. Make a plan of action

V.  Document the Crime Scene

     A.  Record the crime scene and potential evidence with

          1.  Notes – record the following while at the crime scene (details are the key)

               (1) Date

               (2) Time

               (3) Description of the location, weather, and environmental conditions

               (4) Description of the crime

               (5) Location of the evidence relative to other key points

               (6) Names of all people involved

               (7) Any other relevant information

           2. Photography

               (1) Nothing should be moved until photographed

               (2) Take photos of the scene and the surroundings

               (3) Photograph entrances and exits

               (4) Use wide and close-up photos

               (5) Use various angles of each piece of evidence

               (6) Use a ruler to show size

           3. Sketches – draw a rough sketch at the scene (reconstruct a better one later) including

               (1) Date, time, and location

               (2) Scale

               (3) Recovered items

               (4) Important features

               (5) Accurate distance measurements of objects (from two fixed points)

               (6) A legend for the description of items

               (7) A compass designating north

               (8) Names of the investigators, victims, and suspects

          4.  Videography

               (1) Narrate the video

               (2) Be objective

               (3) Record from different perspectives

VI. Measuring Techniques

     A. Triangulation

          1. For each piece of evidence being recorded, use two permanent objects as reference points that are not                   likely to be moved

          2. The two reference points and the piece of evidence form a triangle, hence the term triangulation

          3. Whatever object you are measuring to or from, use the same spot on the object every time

     B.  Rectangular Coordinates – Baseline

          1. The simplest form of the rectangular coordinate system

          2. Using a straight line between two known points, items are measured along the line and then measured                     perpendicular to the line

          3. Inside or outside of a house, this line can be a straight wall

          4. For outdoor scenes, use a string or a long measuring tape as the reference or baseline

     C.  Rectangular Coordinates – Grid

          1. Measure the distance of the items from two perpendicular base lines

          2. This technique is particularly appropriate in a room with perpendicular walls or in the outdoors with                            perpendicular streets

     D.  Polar Coordinates

          1. Measure both the distance and the direction (angle) an object is from a known reference point

          2. For example, 40 feet from the edge of the house and 15 degrees east of north

VII. Search the Crime Scene

     A.  When searching a crime scene wear the following, if available, to minimize contamination

          1. Disposable gloves

          2. Masks

          3. Coveralls with a hood

          4. Slippers

     B.  Search Patterns

          1. Depend on the size and the location of the crime scene and the number of investigators available

          2. Stick to one pattern and one supervisor

          3. It’s better to collect everything and not need it than fail to collect something and need it later

          4. Spiral – may move inward or outward; best used where there are no physical barriers

          5. Grid – basically a double-line search; effective, but timeconsuming

          6. Line (Strip) – best in large, outdoor scenes

          7. Zone (Quadrant) – most effective in houses or buildings; teams are assigned small zones for searchin

VIII. Collect and Package Evidence

       A.  Physical evidence must be packaged and collected before time and weather can alter it

       B. Physical evidence – any object that can establish that a crime has been committed or links a crime and                    the victim or suspect

       C. The Golden Hour – the window of opportunity to collect timesensitive information or evidence

       D. Each item must be placed in a separate container, and sealed and labeled

       E. The most fragile evidence is collected and packaged first

       F. Different types of evidence require specific or special collection and packaging techniques

       G. The body is the property of the coroner or medical examiner; collection of evidence on the body is done by               that department

       H. Containers such as vials, envelopes, plastic bags, paper bags, canisters, and cardboard boxes are good                   packaging devices

       I.  Most items should be placed in a primary container and then in a secondary container

      J. Trace evidence may be placed on a piece of paper which is then folded in a “druggist fold” and placed in a                secondary container

      K. Containers should be sealed with tamper proof tape, and dated and initialed

      L. Each package should contain

          1. Date, time, and location

          2. Case number

          3. Agency and collector’s name

          4. Victim’s name(s)

          5. Description of contents M. Never package two items from two different sources or locations

IX. Chain of Custody

     A. There must be a written record of all of the people who have had possession of an item of evidence,                         beginning at the time of the collection

     B. Every person who has handled or examined the evidence must be accounted for

     C. Chain of Custody should include

          1.. Date and time of transfer

          2. Location of transfer

          3. To/From names

          4. Purpose of the transfer

X.  National Databases

     A.  Crime scene investigators can submit evidence for analysis to several national databases depending on the              type of evidence

     B.  Examples include

          1. Automated Fingerprint Identification System (AFIS)

          2. Integrated Automated Fingerprint Identification System (IAFIS)

          3. Combined DNA Index System (CODIS)

          4. Integrated Ballistics Identification System (IBIS)

          5. International Forensic Automotive Paint Data Query (PDQ)

This information was taken from the Texas Education Agency, 2011.