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CJE2600
Criminal Investigation
Chapter 3
Investigators, the Investigative Process, and the Crime Scene
Learning Objectives
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Understand the role of the investigator and skills and qualities they must possess
Discuss major events in the investigation of a crime
Explain the major steps in a preliminary investigation
Describe activities conducted in a follow-up investigation
Define a crime scene
Outline purposes and functions of an investigator
Chapter Objectives
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Explain the “rules” for the crime scene investigator
Identify potential threats to investigators’ health and safety
Be familiar with major considerations that dominate the crime scene search
Be able to discuss investigation of staged crime scenes
Explain crime scene reconstruction
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The contributions of physical evidence to an investigation are diminished primarily by the inability,
unwillingness, or failure to locate, properly collect, mark, and preserve the evidence, and by the
drawing of improper conclusions from its analysis.
WHAT IS A CRIME?
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A crime is the commission or omission of any act, which is prohibited or required by the penal code
of an organized political state, to which some punishment or sanction is attached.
Classifications
o Felony
 Punishable by death or imprisonment for more than one year in a state prison.
o Misdemeanor
 Punishable by fine and/or imprisonment for up to one year in a local or county jail.
o Infraction or Violation
 Minor offenses punishable by a fine only.
THE INVESTIGATOR
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Someone who gathers, documents and evaluates evidence.
o Strong professional training and experience
o Strong degree of self-discipline
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Uses legally approved & ethical methods
Does not act out of malice or bias
Includes all evidence of innocence as well as guilt
Uses systematic methods of inquiry
Uses both inductive and deductive reasoning
Inductive: From specific details to a general view
 Form a logically consistent explanation of the crime.
Deductive: Creates a hypothesis about the crime.
 Does everything fit together?
Logical fallacies, the failure to consider all alternatives, and bias can lead to untenable
inferences!
THE INVESTIGATOR
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Someone who gathers, documents and evaluates evidence.
o Compassionate, not calloused and cynical
o Has wide ranging contacts across many occupations
o Remains objective at all times
o Leaves nothing to chance during investigation
THE INVESTIGATIVE PROCESS
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Objectives
o Establish if a crime was committed
o Collect, document and preserve evidence
o Identify and apprehend the suspect(s)
o Recover stolen property
o Assist in the prosecution of the person(s) charged with the crime(s)
THE PRELIMINARY INVESTIGATION
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The actions taken at the scene of a crime immediately following its detection and report to the
police
o Receipt of information and initial response
o Crime scene control
o BOLO alerts
o Crime scene determination
o Evidence
o The report
THE PRELIMINARY INVESTIGATION
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Be alert for people/cars leaving crime scene
Approach the scene cautiously
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Assess the scene
o Is violence still ongoing?
o Dangers/special hazards
Determine if a tactical situation exists
Remain alert and attentive
Follow departmental contact protocols
Treat the location as a crime scene until it is concluded otherwise
Emergency Care
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Saving a victim’s life has a higher value than preserving physical evidence
Assess level of injuries to victim and request medical assistance, as necessary
Point out potential evidence to medical personnel
o Do not allow them to cut clothing through or along bullet holes or knife openings
o Document all movement of people and items
Obtain as much information as possible from victim before he/she is moved
Document information from emergency medical personnel
Attempt to get a dying declaration, if possible
Secure and Control Persons at Scene
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Identify boundaries of the crime scene and secure
Identify possible or actual lines of approach to, and flight from the scene
Maintain crime scene control
o Identify all individuals
o Keep a crime scene entry log
o Protect scene
o Set up physical barriers
Separate any potential combatants and any persons arrested
Ask witnesses not to discuss the story together
General Evidence Procedures
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Smaller agencies, responding officer must recognize, identify, locate, and collect physical evidence.
Chain of custody must be established.
Prepare offense/incident report.
If investigators responding
o Brief them
o Assist in controlling scene
o Remain at scene until relieved.
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FOLLOW-UP INVESTIGATION
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Subsequent investigation
o Become thoroughly conversant on case
 Read reports
 View photos, videos, audio
o Contact witnesses
o Checking out suspect(s) alibi
o Gathering additional evidence from other locations
o Talk with informants
o Attempt to locate additional witnesses
o Conduct area canvasses
o Evaluate evidence collected and laboratory results of tests
o Obtain search and/or arrest warrants
o Recover stolen property
o Confer with prosecutor
Case closure
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Exceptionally cleared
o It can be shown who committed the crime, but for any of several reasons the case cannot be
pursued further
 Suspect dead
 Victim refuses to cooperate
 State declines to prosecute
Cleared by arrest
o Perpetrator arrested and sufficient evidence to file criminal charges
CRIME SCENE
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Location where the offense was committed
o May include surrounding areas where evidence may be located
o Always start big . . . It’s much easier to make it smaller than to expand it at a later time
o There may be more than one crime scene
Crime Scene continued
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Primary crime scene
o The location where the initial offense was committed
Secondary scenes
o All subsequent connected events
Macroscopic
o “Large view”
 Body(ies), rooms, cars, buildings
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Microscopic
o Specific objects and pieces of evidence
 Knives
 Bite marks
 Hairs and fibers
 Shoe and tire impressions
Crime Scene continued
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Crime-scene investigators examine blood-stained clothes before placing them in an evidence bag.
ORGANIZATION OF THE CRIME SCENE
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Overall coordination
o Handled by assigned senior investigator
o Power to call in additional resources & coordinate all investigative activities
 Medical examiner
 Media liaison
Technical services
o Crime laboratory personnel & supervisors
Investigative services
o Interviewing witnesses and victims
o Neighborhood canvass
o Suspect field interrogations
CATEGORIES OF EVIDENCE
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Corpus Delicti evidence
o Evidence that helps to prove the elements of the crime(s)
o The principle that a crime must have been proven to have occurred before a person can be
convicted of committing that crime
Associative evidence
o Evidence that connects the suspect to the scene and/or victim or connects the scene/victim
to the suspect
 It is bidirectional
Trace evidence
o Small or microscopic evidence, or evidence in limited amounts
Rules for the Crime Scene Investigation
CRIME SCENE CONTROL
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The actions which the first arriving officer at the crime scene takes to make sure that the integrity of
the scene is maintained.
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Control also includes preventing people at the scene from becoming combatants and separating
witnesses.
Rules for the Crime Scene Investigation
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Maintain Control
o Without control a life might be lost, evidence destroyed, assignments overlooked, or the
investigation conducted in a generally slovenly manner.
 Manage media
 Release only information that is necessary
Rules for the Crime Scene Investigation
CONCEPTUALIZATION
Keep known facts AND inferences in mind when processing scene
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Facilitates reconstruction of the offense
Identification of the modus operandi
Identification of certain types of evidence
Assists in establishing investigative direction
Rules for the Crime Scene Investigation
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Conceptualize Events
o Be careful not to impart one’s own probable motives or actions to the perpetrator without
grounds to do so
o Locate trace evidence
 Is extremely small or limited amounts
 Alternative light systems (ALSs)
 Various colored lights cause many types of evidence to fluoresce
o Glass and metal fragments
o Bite marks
o Bruises
o Human bone
Rules for the Crime Scene Investigation
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Caution
o Extremely important evidence may be altered or destroyed
 Don’t destroy evidence
o The area to be searched may be too rapidly defined
 Make crime scene bigger than expected and shrink as necessary
o Other areas that might be fruitful are overlooked or given only a cursory examination
 Don’t overlook fruitful areas for exploration
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Do more than a cursory examination
INCLUSIVENESS
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Obtain every piece of evidence
If not sure, take it as evidence until it is ruled out
Do not dismiss items of possible evidence
Standard samples and elimination prints should be obtained
o Be careful of rationalization and fatigue
DOCUMENTATION
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Constant Activity
o Starts with rough shorthand field notes
o Sketches
o Diagrams to scale
Ways to document a crime scene visually include:
o Video taping
o Photographing
o Sketching
LOGS
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EVIDENCE RECOVERY LOG
o A chronological record of who found what evidence, where, witnessed by whom, and
notations about other ways the evidence may have been documented, e.g., photography
ASSIGNMENT LOG
o Details who is assigned to what function and the sequence of events at the scene
PHOTOGRAPHIC LOG
o Details who took which shots, from where, when, and under what circumstances
EVIDENCE RECOVERY LOG
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The evidence recovery log is an important document which records all pieces of physical evidence
found at a crime scene. This is critical if the case is to be successfully prosecuted later.
THREATS TO INVESTIGATORS HEALTH AND SAFETY AT CRIME SCENES
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Insect bites
HIV/AIDS
o Human bites, needle sticks, cuts
o “Weeping” lesions
Hepatitis B and C
o Spread by contact with blood of an infected person
Tuberculosis
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o Airborne
Use Personal Protection Equipment
MAJOR CONSIDERATIONS OF THE CRIME SCENE SEARCH
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Boundary Determination
o Set up an inner and outer perimeter
o Consider primary and any secondary crime scenes
 Perpetrator’s lines of approach to and from scene
Inner perimeter
o Specific items of evidence are know to be
Outer perimeter
o Set farther back than inner to help establish control of, and entry into, the scene
MAJOR CONSIDERATIONS OF THE CRIME SCENE SEARCH
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Choice of Search Patterns
o The crime scene coordinator may choose from a variety of crime scene search patterns
based upon the type and size of the crime scene.
CRIME SCENE SEARCH PATTERNS
There are 5 basic search patterns
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Spiral
Strip/Line
Grid
Zone/Quadrant
Pie/Wheel
MAJOR CONSIDERATIONS OF THE CRIME SCENE SEARCH
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Instruction of Personnel
o Brief all involved personnel on case, method of search, action to take when evidence is
located
MAJOR CONSIDERATIONS OF THE CRIME SCENE SEARCH
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Coordination
o Integrating efforts of those assigned to the technical (CSIs) and investigative service
functions
o Other agencies (police, state attorney/legal)
o Interdepartmental (fire-rescue, medical examiner)
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MAJOR CONSIDERATIONS OF THE CRIME SCENE SEARCH
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Suspension of search
o Depends on complexity of case
o Abundance or scarcity of physical evidence
o Available personnel
Crime scene release
o Should be well thought out
o Meet with all team members first
o Generally, only have one opportunity to process a crime scene
 Any mistakes made may not be rectifiable
o Photograph scene
Crime Scene
Police diver recovers a handgun as part of an underwater investigation.
Evidence Collection
1. Identify each item of evidence collected or handled
2. Describe the location and condition of the evidence at the time collected
3. State who had contact with or handled the evidence
4. State when, or during what time periods, the evidence was handled
5. Declare under what circumstances, and why, the evidence was handled
6. Explain what changes, if any, were made to the evidence
Visual Documentation
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Three major methods
o Digital Video Recording
o Digital Still Photography
o Sketching
Visual Documentation
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Digital Video Recording
o Motion of video holds attention of viewers
o Are not, however, an acceptable alternative to high-resolution digital photographs
o Be careful not to record unwanted and potentially embarrassing extraneous comments
o Once recording begins, camera should be kept running; gaps may be hard to satisfactorily
explain to jurors
o Most common mistake is going too fast
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Digital Video Recording
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Keep the lens clean
Use battery packs instead of cords
Begin recording with an identification
Pan the crime scene area 360 degrees
Use a rolling tripod or shoulder brace for smoother pictures
Digital Still Photography
Four classes of photographs that must be taken with digital still cameras:
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Orientation
o Long/longer range shots, general views of the entire scene.
Relationship
o Medium range, photos of evidence and their positional relationship to each other
Identification
o Close-ups that show specific features,
 such as the serial number on a firearm
Comparison
o Close-ups that document characteristics for future laboratory examination
o Such as shots of developed fingerprints
Digital Still Photography (continued)
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Photograph the scene as soon as possible
Prepare a photographic log that records all photographs and a description and location
Photograph from eye level to represent the normal view
Photograph the most fragile areas of the crime scene first
Photograph all stages of the crime scene investigation including discoveries
Photograph the condition of evidence before recovery
Take all photographs intended for examination purposes without a scale, and then with one
Photograph the interior crime scene in an overlapping series using a normal lens; use a wide-angle
lens for overall photographs
Digital Still Photography (continued)
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Photograph exterior scene, using overall photographs including a landmark.
Photograph entrances and exits from the inside and outside
Photograph important evidence twice
Median-distance that shows evidence and its position to to other evidence
Close-up that includes a scale and fills the frame
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Visual Documentation
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Sketching
o A basic diagram of the crime scene showing important points
 Locations where various pieces of physical evidence were located
Crime Scene Sketching and Forensic Mapping
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Crime scene sketch
o Rough sketches: made by hand at the scene
o Smooth or finished sketches: drawn at the office—either by hand or by specialized
computer software
Forensic mapping
o The process of taking and recording the precise measurements of items of evidence to be
drawn or fixed on the sketch
o Allows the positioning of the evidence back into its original location with a reasonable
degree of accuracy
o Errors call into question the accuracy of the sketch as well as the investigation as a whole
Crime Scene Sketching and Forensic Mapping (continued)
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Overhead or bird’s-eye view
o Most common
Elevation view
o Shows heights
Cross-projection view
o Lays the walls to a room down so objects of interest in the wall can be mapped
Mapping Methods
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Rectangular Coordinates
o Used with scenes having clear and specific boundaries, such as interior walls
 Can be measured fast and accurately
 Sonic, laser, or infrared measuring device
Triangulation
o Used for both interior scenes in buildings, as well as for outdoor scenes, where
measurements must spring from distinct, permanent features or landmarks, such as the
corner of a home, telephone, mailbox, and lighting poles
Mapping Methods (continued)
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Baseline Coordinates
o Similar to rectangular coordinates process
o Used both inside and outside
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Mapping Methods (continued)
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Polar Coordinates
o Used for mapping outdoor scenes at which evidence is scattered over a fairly large open
area
o Datum point
 Starting point
 Steel rod is driven into the ground
Grid System
o Used when there is a large outdoor scene with no significant features or landmarks
o Use datum point
Laser Scanning
Panoramic Cameras
Submitting Evidence to the Crime Laboratory
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The investigator’s name, agency, address, telephone number, and email address.
Copies of any previous correspondence about the case, including any pertaining to other evidence
that was examined earlier.
The type of criminal act and the basic case facts related to each item of evidence.
The name(s) and descriptive data about the individual(s) involved (subject, suspect, victim, or a
combination of those categories) and the agency assigned case number.
Submitting Evidence to the Crime Laboratory (continued)
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A list of the evidence being submitted.
What type(s) of examination is requested.
Where the evidence should be returned and where the laboratory report should be sent.
A statement if the evidence was examined by another expert in the same field, if there is local
controversy, or if other law-enforcement agencies have an interest in the case.
Any reason(s) justifying an expeditious examination request.
The name and locator information for the assigned prosecutor, if designated already.
Investigative Success
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Law enforcement considers a case successful if it can be administratively classified:
o “Cleared by exceptional means”
o “Cleared by arrest”
End of chapter 3