Observations vs. Inferences

Chapter Goal & Assessment

• To demonstrate the following skills in the processing of a crime scene

1. Securing the crime scene

2. Documenting the scene

3. Collecting & packaging evidence

Unit 2: THE CRIME SCENE

“Oh, how simple it would all have been had I been here before they came like a herd of buffalo and wallowed all over it.”

—A. Conan Doyle, in The Boscombe

Valley Mystery, 1892

CRIME SCENE

You will learn: The steps to take when

processing a crime scene. That type of evidence

determines what packaging should be used.

Why the chain of custody must be preserved.

You will be able to: Isolate, record, and search for

evidence at a mock crime scene.

Collect and package evidence at a mock crime scene using to proper forensic procedures.

CRIME SCENE TEAM

A group of professional investigators, each trained in a variety of special disciplines.

Team Members First Police Officer on the scene Medics (if necessary) Investigator(s) Medical Examiner (if necessary) Photographer and/or Field Evidence Technician Lab Experts

PROCESSING ACRIME SCENE

Isolate and secure the scene

Record/Document the scene

Collect and package evidence, maintaining the chain of custody

Submit evidence to the crime lab

Overview of Duties

FIRST OFFICERON THE SCENE

• Assist those hurt: may destroy evidence, but saving someone takes priority

• Assess the crime scene: give consideration to offenders approach and flight path

• Detain the witness(s)

• Protect the crime scene: establish a boundary that is too large, then collapse it later. Limit access (even to other officers) and create log of people on the scene

• Take notes: more on this later…

• Make appropriate notifications: ME, CSIs,

Investigators

CRIME SCENE SURVEYperformed by the CSI

Interview the first responding officer to find out details Determine what is usable and relevant evidence (experience helps with

this) Observations:

Walk through to develop a mental plan of how the scene should be handled Oblique lighting: technique used indoors to reveal items not visible under

ordinary light Documentation & Recording duties:

Notes Photographs/Video Sketches

Search, Collect, and Package evidence

SEARCH METHODS

One person should be responsible for supervising collection of evidence

Line or strip method—best in large, outdoor scenes Grid method—basically a double-line search; effective,

but time-consuming Zone method—most effective in houses or buildings;

teams are assigned small zones for searching Wheel or ray method—best on small, circular crime

scenes Spiral method—may move inward or outward; best used

where there are no physical barriers

DOCUMENTATION

Notes extremely important, forces observation Weeks, months, years later Should Include:

date and time, description of the location, weather and environmental conditions, description of the crime, location of the evidence relative to other key points, the names of all people involved, modifications that have occurred and other relevant information

CRIME SCENE SKETCH

*** Review the supplemental handout on Sketching ***

Importance of the crime scene sketchImportance of the crime scene sketch

•compliments the photographs by giving spatial relationships

•Communicates information that words cannot describe

•Can be drawn to selectively include only relevant material (confusing detail can be eliminated)

•Better overall depiction of the scene

•Easy to show travel routes of suspects, victims and vehicles

CRIME SCENE SKETCH

Date: August 14, 2005 Criminalist: Ann WilsonTime: 11:35 am Location: 4358 Rockledge Dr, St. Louis, Mo.

N

*** Review the supplemental handout on Sketching ***

CRIME SCENE SKETCH

*** Review the supplemental handout on Sketching ***

Types of Crime Scene SketchesTypes of Crime Scene Sketches

Baseline – useful outside or in area with aisles

Rectangular Coordinate – easiest and most common

Triangulation – 2 fixed points and form a triangle

Polar Coordinate – very difficult

We will learn to use …. Baseline and Rectangular Coordinate

CRIME SCENE SKETCH

*** Review the supplemental handout on Sketching ***

Sketching on the SceneSketching on the Scene

Important:

Rough vs. Clean

Get all you information and details…do not worry about it being pretty…you can clean it up when you get back to the office!

DOCUMENTATION

Notes—date and time, description of the location, weather and environmental conditions, description of the crime, location of the evidence relative to other key points, the names of all people involved, modifications that have occurred and other relevant information

Photography—photos of scene and surroundings, far, mid-range to close-up photos with 90 degree and various angles of each piece of evidence, photos as viewed by any witnesses.

Sketches—inclusion of date, time, scale, reference points, distance measurements, names of investigators, victims, suspects, and a legend (key)

Evidence Collection - packaged, marked, sealed, and preserved in a consistent manner

Videography—allows narration (non-subjective) to be included

ROUGH SKETCH TO FINAL SKETCH

This is what I made at the scene.

This is what I made at the office.

ROUGH SKETCH TO FINAL SKETCH

Put your measurements on your sketch

Use two perpendicular surfaces to make your measurements.Usually these are two walls

Use a method to indicate which direction the measurements are made

10 ‘ S and 7 ‘ E

10 ‘ X 7 ‘ Y

10 ‘ 7 ’

Rectangular Coordinate Sketching Method

Baseline Sketching Method

Pick a reference point

Make a straight reference line

Make 90 degree measurements from the reference line showing direction

Baseline Sketching Method

Cumulative vs. Consecutive Measurements

Cumulative method

anchor the tape at one end and measure all the points from that reference point Less likely to result in an error

Consecutive method

measures from one point to the next point and so on…with this method if you have an incorrect measurement the others are wrong too*****DO NOT USE *****