This document provides an overview of criminal investigation and identification. It discusses the goals of criminal investigation as identifying, locating, and providing evidence of guilt of the offender. The primary job of an investigator is to determine what offense was committed by answering who, what, when, where, why, and how. Identification of criminals can occur through confession, eyewitness testimony, circumstantial evidence, associative evidence, or modus operandi. Gathering evidence and using tools like interviews, interrogation, and instrumentation are also discussed.

1. NOTES ON CRIME DETECTION AND INVESTIGATION
CDI-1: FUNDAMENTALS OF CRIMINAL INVESTIGATION
CRIMINAL INVESTIGATION – is an art which deals with the identity and location of the
offender and provides evidence of guilt through criminal proceedings.
INVESTIGATION DEFINED: The collection of facts to accomplish a three-fold aim:
a. to identify the guilty party;
b. to locate the guilty party; and
c. to provide evidence of his guilt.
PRIMARY JOB OF AN INVESTIGATOR
The primary job of the investigator is to discover whether or not an offense has been
committed under the law, after determining what specific offense has been committed, he must
discover how it was committed, by whom, where it was committed, when and why it was
committed (Cardinal points of Investigation 5W’s and 1H).
SIX CARDINAL POINTS OF INVESTIGATION
WHAT specific offense has been committed? Nature of crime
WHERE crime was committed? Place or location
WHEN it was committed? Time and date
WHOM it was committed? Persons/s involved
WHY it was committed? Reason or motive of
Committing the crime
HOW it was committed? Manner, method or modus
operandi
QUALITIES OF A GOOD INVESTIGATOR
1. Perseverance
2. Intelligence
3. Honest
4. Understanding of the people and environment
5. Keen power of observation
TRAINING
Training, as one of the foundations of investigation, is concededly a vital ingredient in the
creation of a total investigator. Experience alone does not make one good investigator. Many
who had been hostage to this notion often ended in jeopardy. The ideal conjugal partnership is
training and experience. The fusion of the best training and vast experience is a formidable
force that can threat even the most sophisticated technology and syndicated crimes. The
necessity of training as a purveyor of change builds the investigator’s confidence. It widens his
vision for professional growth and strengthens his will to survive and prevail over crises.
The National Forensic Science Training Institute (NFSTI) under the Philippine Public
Safety College is the institution that trains uniformed personnel of the Philippine National Police
to become a certified investigator.

2. THREE TOOLS OF INVESTIGATION
1. INFORMATION
It is the knowledge/data which an investigator acquired from other persons and records.
Classes of Information
a. Regular Sources – records, files from government and non-government agencies, news
items.
b. Cultivated Sources – information gathered upon initiative of the investigator from
informants, vendors, taxicab driver, GRO, and others.
c. Grapevine Sources – these are information coming from the underworld characters
such as prisoners and ex-convicts.
2. INTERVIEW AND INTERROGATION
INTERVIEW – Is a conversation with a purpose, motivated by a desire to obtain certain
information from the person being interviewed as to what was done, seen, felt, heard, tasted,
smell or known.
This is the questioning of a person believed to possess knowledge that is in official
interest to the investigator.
BASIC ASSUMPTIONS
Nobody has to talk to law enforcers. No law compels a person to talk to the police if he
does not want to. Therefore, people will have to be persuaded, always within legal and ethical
limits, to talk to law enforcers. This makes interviewing an art.
I.R.O.N.I.C. FORMAT
The interview of a witness can be described by its acronym ‘IRONIC’ which stands for
Identity, Rapport, Opening Statement, Narration, Inquiry, and conclusion.
Identity – prior to the commencement of an interview, the investigator should identify
himself to the subject by name, rank and agency. Except, when there is no need to know the
officer’s identity.
Rapport – it is good to get the positive feeling of the subject towards the investigators,
such friendly atmosphere is a vital for both the subject and the investigator t have a better
interaction.
Opening Statement – the investigator must have to indicate why the subject is being
contracted.
Narration – the witness should be allowed to tell all he knows with little interruptions
from the investigator.
Inquiry – after all information have been given by the subject, that is the time for the
investigator to as question to clarify him about the case under investigation.
Conclusions – after the interview, it is but proper to close the interview with outmost
courtesy and thanking the subject for his cooperation.
RULES TO BE OBSERVED IN QUESTIONING
a. One question at a time
b. Avoiding implied answer
c. Simplicity of the questions
d. Saving faces
e. Avoid close ended questions (yes or no)

3. INTERROGATION –is a questioning of a person suspected of having committed an
offense or a person who is reluctant to make full disclosure of information in his possession
which is pertinent to the investigation.
What are the purposes of Interrogation?
a. To obtain confession to the crime
b. To induce the suspect to make admission
c. To learn the facts of the crime
d. To learn the identity of the accomplice
e. To develop information which will lead to the recovery of the fruits of the crime
f. To discover the details of other crimes participated by the suspect
INTERROGATION TECHNIQUES
Emotional Appeal
Place the subject in the proper frame of mind. The investigator should provide emotional
stimuli that will prompt the subject to unburden himself by confiding. Analyze the subject’s
personality and decide what motivation would prompt him to tell the truth, and then provide
those motives through appropriate emotional appeals.
Sympathetic appeal
The suspect may feel the need for sympathy or friendship when he is apparently in
trouble. Gestures of friendship may win his cooperation.
Kindness
The simplest technique is to assume that the suspect will confess if he is treated in a
kind and friendly manner.
Extenuation
The investigator indicates he does not consider his subject’s indiscretion a grave
offense.
Shifting the blame
The interrogator makes clear his belief that the subject is obviously not the sort of person
who usually gets mixed up in a crime like this. The interrogator could tell from the start that he
was not dealing with a fellow who is a criminal by nature and choice.
Mutt and Jeff
Two (2) Agents are employed.
- Mutt, the relentless investigator, who is not going to waste any time because
he knows that the subject is guilty.
- Jeff, on the other hand, is obviously a kind-hearted man.
Bluff on a Split Pair
This is applicable when there is more than one suspect. The suspects are separated and
one is informed that other has talked.
Pretense of Physical Evidence
The investigator may pretend that certain physical evidence has found by laboratory
experts against him.
Jolting
May be applied to calm and nervous subjects by constantly observing the suspects, the
investigator chooses a propitious moment to shout a pertinent question and appear as though
he is beside himself with rage. The subject may be unnerved to the extent of confessing:

4. CUSTODIAL INTERROGATION/INVESTIGATION – is the questioning of a law
enforcement officer on a person under custody and otherwise deprived of his freedom or liberty.
This is the stage in investigation where there is strict observance of the Miranda Doctrine.
MIRANDA DOCTRINE – this case which entitled Miranda vs. Arizona, is a US Supreme
Court Jurisprudence which laid down the constitutional rights of the accused during custodial
investigation. It was incorporated in our 1973 Constitution and later in the 1987 Constitution of
the Philippines.
3. INSTRUMENTATION
It is the application of instruments and methods of physical science to the detection of
crimes. In cases where there are no significant physical evidence to be found, then the use of
instrumentation is relatively unimportant.
PHASES/STAGES OF CRIMINAL INVESTIGATION
1. Identification of criminals
2. Tracing and locating the criminal
3. Gathering of evidence to prove the guilt of the criminal
1. IDENTIFICATION OF CRIMINALS
METHODS OF IDENTIFYING CRIMINALS
a. By confession or admission of the criminal himself
b. Identification by accounts or testimonies of eyewitnesses
c. Identification by circumstantial evidence
d. Identification by associative evidence
e. Identification by the Method of Operation (Modus Operandi)
CONFESSION– is the direct acknowledgement of guilt arising from the commission of a crime.
Types of Confession
a. Extra-Judicial Confession – those made by the suspect during custodial investigation.
b. Judicial Confession– those made by the accused in open court. The plea of guilt may
be during arraignment or in any stage of the proceedings where the accused changes
his plea of not guilty to guilty.
ADMISSION– is a self-incriminatory statement by the subject falling short of an
acknowledgement of guilt. It is an acknowledgement of a fact or circumstances from which guilt
maybe inferred. It implicates but does not incriminate. It is also an acknowledgement that a fact,
action or circumstances are true which strongly infer or directly admit guilt but lacks the detail of
the elements of the crime.
RULES TO BE OBSERVED IN TAKING CONFESSION OR ADMISSION
1. Confession or admission must be taken preferably in writing and under oath
2. It must be written in the language known and understood by the accused, if not it must
be clearly translated
3. It must be freely and voluntary given by the accused

5. 4. Under the New Constitution, it must be taken in the presence of competent and
independent counsel chosen by the accused
KINDS OF CRIMINALS IDENTIFIED BY WITNESSES
a. Known criminals
b. Unknown criminals
Methods of Identification by witness
a. Verbal description
b. Photographic files (Rogues Gallery)
c. General Photograph
d. Artist sketch (Composite Criminal Illustration)
The value of identification by eyewitness depends on:
a. The ability to observe and remember distinct appearance of suspect;
b. Prevailing condition of visibility;
c. The lapse of time.
What are the procedures of identification by eyewitness?
a. Physical line-up – is a means of selecting a suspect from a group of innocent
persons usually composed of seven to ten persons. The purpose of line-up is to
eliminate the power of suggestion.
b. Physical show-up – only one person is shown to the witness usually at the scene of
the crime and made immediately after the arrest of the suspect.
CIRCUMSTANTIAL EVIDENCE - facts or circumstances from which, either alone or in
connection with other facts, the identity of the person can be inferred.
What must be inferred to prove identity by circumstantial evidence?
a. Motive – is what induces the criminal to act
b. Intent –is the result or accomplishment of the act
c. Opportunity –is the physical possibility that the suspect could have committed the
crime.
It could be inferred from the following:
a. The suspect could have been in the vicinity of the crime scene at the time it was
committed.
b. Knowledge of the criminal objective.
c. Absence of an alibi on the part of the criminal.
PHYSICAL EVIDENCE TO IDENTIFY CRIMINALS
1. CORPUS DELICTI– is the body of the crime or fact of specific loss or injury sustained. It
constitutes the essential parts or elements in the commission of the crime.
2. ASSOCIATIVE EVIDENCE – these are the pieces of evidence that will link the suspect
to the crime scene. The suspect may leave some clues at the scene such as weapons,
tools, garments or prints.
3. TRACING EVIDENCE – articles which assist the investigator in locating the criminal.
Stolen goods in the possession of the suspect in an example of tracing evidence.
MODUS OPERANDI – is the method of operation by a specific criminal or criminal syndicate. It
is a distinct pattern of how a crime is committed and is established by a series of crimes under
one classification. The modus operandi of one criminal is distinct and different from the other. It
is a criminal trademark, logo or brandname.

6. 2. TRACING AND LOCATING THE CRIMINALS
INFORMANT – is a person who gives information to the police relevant to a criminal case about
the activities of criminals or syndicates.
TYPES OF INFORMANTS
a. Anonymous informant – do not wish to be identified.
b. Rival elimination informant – to eliminate competition.
c. False informant – reveals information of no consequence or value.
d. Frightened informant – motivated by anxiety.
e. Self-aggrandizing – hangs about the fringes of the criminals.
f. Mercenary informant – gives information for a price.
g. Double crosser informant – to get more information from the police.
h. Woman informant – female associate of the criminals.
i. Legitimate informant – operators of legitimate business establishments.
MOTIVES OF INFORMANTS
a. Vanity
b. Civic-mindedness
c. Fear
d. Repentance
e. Avoidance of punishment
f. Competition
g. Revenge
h. Jealousy
i. Remuneration
SURVEILLANCE – is the secret observation of persons, places,and vehicles for the purpose of
obtaining information concerning the identities or activities of the subject.
a. Surveillance of Place (fixed/ stake-out)
b. Shadowing
c. Roping
SURVEILLANT – is the person who maintains the surveillance or performs the observation.
SUBJECT – the person or place being watched or surveyed.
KINDS OF SURVEILLANCE
1. Surveillance of places
2. Tailing or shadowing
3. Undercover investigation or roping
How to conduct surveillance of place?
A careful survey of the surrounding area should be made. The character of the
neighborhood, residents and transient should be noted. The observation point should be
selected properly. When observation is conducted from a ‘plant’, surveillance agents must be
extremely careful not to reveal their true activity. Observation maybe made through a window or
other aperture so as to be unnoticed from the outside. Venetian blinds afford the best coverage,
but may appear to be out of place of some buildings. An alternative is to lower the roller of draw
shades another inch from the window. Binoculars are generally essentially equipment of the

7. plants, as they facilitate positive identification of person entering or leaving the place under and
observation. A still or video camera with telephoto lens can also be used effectively. Agents
should take careful notes of what they observe and should record detailed descriptions of all
individuals entering the target. A chronological log is usually the best of recording pertinent
occurrences.
TAILING OR SHADOWING – is the act of following a person, depends on the number of
surveillant available, volume of pedestrian traffic and importance of concealing the surveillance.
METHODS OF SHADOWING
a. One man –extremely difficult and should be avoided, if unavoidable keep subject in
view at all times.
b. Two man – two agents are employed to follow the subject.
c. ABC method – reduces the risk of losing the subject, affords greater security agents
detection.
d. Progressive/Leap from method – poor chances of obtaining good results, agents
are stations at a fixed point assuming that subject followed the same general route
each day.
e. Combined foot-auto surveillance – employment of surveillants on foot and agents
in an automobile.
What are the things that should be avoided during shadowing?
a. Don’t meet the eye of the subject
b. Don’t adopt a slinking, sleuthing, creeping manner
c. Don’t wear story book disguises
d. Don’t carry noticeable items
e. Don’t greet fellow agents
f. Don’t make notations ostensibly
How to detect foot surveillance?
A subject who is suspicious of being under surveillance may resort to trickery in order to
verify his suspicion. When a subject resort to such trickery, it is good policy to change agents,
for the suspect may have ‘spotted’ one or more of his surveillants.
a. stopping abruptly and look back
b. casually looking around
c. reversing course/retracing steps
d. boarding bus and alighting just before they start
e. riding short distance on bus
f. circling the block on a taxi
g. entering a building and leaving immediately via another exit
h. stopping abruptly after turning a corner
i. using convoys
j. watching reflection in shop windows
k. walking slowly and rapidly at alternate intervals
l. dropping a piece of papers to see if anyone retrieves it
m. stopping to tie a shoe string, meanwhile looking around for surveillants
n. arranging with a friend in a shop, stores or other places to watch for surveillants.
How to elude foot surveillance?

8. Common method to elude foot surveillance in which surveillants must be prepared and
guard against are the following:
a. jumping off a bus, trains just as the doors are about to close
b. leaving a building through the rear or side exits
c. losing one self in crowds
d. entering theaters and leaving immediately through an exit
e. pointing out one surveillant to a police to a generally require the agent to explain his
action
f. using decoys
g. taking the last taxi at a stand
h. changing clothing
AUTOMOBILE SURVEILLANCE
The methods of auto surveillance to be used depends upon the numbers and type of
surveillance vehicles available, the volume of vehicular traffic in the area, the importance of
concealing the surveillance from the subject, and the subject’s estimated ability to detect and
elude surveillance. At all times each vehicle should be occupied by at least two agents; one to
concentrate on driving, and the other to observe, take notes, operate radio equipment, or to
dismount and continue the surveillance on foot.
How to detect automobile surveillance
As in the case of foot surveillance, a subject who believes he is being followed may
resort to trickery in order to verify his suspicions. Some of the common tricks employed:
a. Alternate fast and slow driving
b. Driving into dead-end streets
c. Frequency parking
d. Committing flagrant traffic on one way streets, and running through red lights
e. Stopping suddenly around curves or corners
f. Pulling into driveways
g. Speeding up a hill, then coasting slowly down
How to elude automobile surveillance
a. Committing traffic violations
b. Using double entrances to driveways; in one and out the other
c. Curbing through parking lots
d. Driving through congested areas
e. Deserting the vehicle behind curves or corners, but permitting the drivers to drive on
as a decoy.
UNDERCOVER INVESTIGATION – is a form of investigation in which the investigator assumes
a different and unofficial identity in order to obtain information.
DEFINITIONS
a. Undercover- an investigative technique in which the Agent’s/Investigator’s official
identity is concealed to accomplish an investigative mission.
b. Natural cover- using the individual’s true identity, occupation or profession.
c. Artificial cover- the manufacture of documents, false documents, passports, or
forged documents.

9. 3. GATHERING EVIDENCE
CRIME SCENE INVESTIGATION
It is the conduct of processes, more particularly, the recognition, search, collection,
handling, preservation and documentation of physical evidence to include the identification and
interview of witnesses and the arrest of suspect/s at the crime scene.
SOCO (Scene of the Crime Operation) – Republic Act6975 as Amended by Republic Act 8551
(PNP Law). The former law placed the Philippine National Police Crime Laboratory as an
Operational Support Unit. The Crime Laboratory established the so-called Scene of the Crime
Operation (SOCO) which is field operation. This is now an innovation because the SOCO now
gathers all evidence at the crime scene and takes custody of them, marking and tagging them
which otherwise the duty of the criminal investigator before.
What Constitute a Crime Scene?
a. Crime scene can be understood to include all areas in which the criminal, any possible
victim and any eyewitness move during the time the crime was committed.
b. The boundaries must be established so that the entire crime scene can be effectively
preserved.
c. In some crimes, however, the crime scene may actually comprise several different sites.
GOLDEN RULE AT CRIME SCENE INVESTIGATION
Never touch, move, or alter any object at the crime scene unless it has been
photographed, measured, and sketched from any conceivable angle.
UPON RECEIPT OF THE CRIME INCIDENT
1. The Desk Officer shall:
a. Record the date and time the report/complaint was made, the identity of the
person who made the report, place of the incident and a synopsis of the incident.
b. Inform his superior officer or the duty officer regarding the report.
2. The First Responder shall:
a. Cordon off the crime scene with whatever available materials like ropes, straws,
human barricade, police line, etc.;
b. Evacuate injured persons to the nearest hospital;
c. Prepare to take the “dying declaration” of severely injured person, if any;
d. Prevent entry/exit of persons within the cordoned area; and
e. Prepare to brief the investigator of the situation upon their arrival.
CRIME SCENE INVESTIGATION PROPER
A. Receipt of Briefing and Designation of Command Post
Command Post – an area which, is ideally located adjacent to the Crime Scene where
the CSI Evidence Custodian stays and receives the pieces of evidence turned over to him
for safekeeping by the other evidence collectors.
B. Initiation of Preliminary Survey (Team Leader of CSI or SOCO)
a. Makes a general assessment of the scene;
b. Takes a cautious walk- through of the crime scene;
c. Takes down extensive note to document important factors;

10. d. Establishes the evidence most likely to be encountered;
e. Defines the extent of the search area;
f. Determines the personnel and equipment needed and makes specific
assignments; and
g. From his assessments, he develops a general theory of the crime scene.
C. Preparation of Narrative Report
The Team leader uses the systematic approach in making a narrative report.
D. Documentation of the Crime Scene
The photographer begins taking photographs as soon as possible. The evidence
collectors do not touch or moved any evidence once it is located until it has been identified,
measured and recorded.
PHOTOGRAPHING THE CRIME SCENE
The main objective crime scene photography is to create an accurate objective visual
record of the crime scene before any item ismoved as possible physical evidence.
MAJOR TYPES OF PICTORIAL VIEWS
1. General View or Long-Range – photograph of the over-all scene.
Distance: From the doorway to the room and other corners of the room
2. Mid-Range View
Distance: Eight or ten feet from the victim
3. Close-up View – every physical evidence must be photographed in close-up view
and for different angles.
CRIME SCENE SKETCHES
A rough sketch is prepared indicating the actual measurement of things with scale and
proportion observed and oriented to the North Pole. All necessary information is placed in the
sketch.
ELEMENTS OF SKETCH
a. Measurement
b. Compass direction
c. Essential items
d. Scale and proportion
e. Legend
f. Title
SPECIFIC KINDS OF SKETCHES
a. Sketch of Locality- give picture of the scene, the crime and its environs, including
neighboring buildings, roads, etc.
b. Sketch of the Ground- picture of the scene of the crime with its nearest physical
surrounding.
c. Sketch in Details – the immediate scene only.
d. Exploded/ cross projection – gives the clear impression of the scene in cases
where blood stains or bullet holes are found.
SKETCHING METHODS
a. Neighborhood sketch
b. Elevation Sketch

11. c. Floor Plan Sketch
d. Detailed Sketch
TYPES OF MEASUREMENTS
1. Rectangular coordinates method – a sketching method that involves measuring
the distance of an object from two fixed lines at right angles to each other.
2. Triangulation method – a sketching method that requires measuring the distance of
an object along a straight line from two widely separated fixed reference points.
3. Baseline method– a sketching method that makes measurements along from a
single reference line, called a baseline, which can be established by using a length of
string, chalk line, or some other convenient means.
4. Compass point method– a sketching method that requires a protractor or some
method of measuring angles between two lines. One point is selected as the origin
and a line extending from the origin becomes an axis from which the angles can be
measured.
5. Cross projection method – a sketching method in which the ceiling appears to
open up like a lid of a hinged box, with the four walls opening outward.
Measurements are then indicated from a point on the floor to the wall.
CRIME SCENE SEARCH
A crime scene search could only be started after it has been photograph and sketched to
systematically look for physical evidence that may prove useful in establishing that a crime has
been committed and to determine what method of operation the perpetrator may have used.
METHODS OF SEARCH
a. Strip or Line Search Method – the searchers will proceed at the same pace along
the path parallel to one side of the rectangle.
b. Double Strip or Grid Method – is a combination of the strip search and is useful for
large crime scene.
c. Spiral or Circular Method – the searchers will follow each other in the path of a
spiral, beginning in the outside and spiraling towards the center or vice versa in a
clockwise or counter clock-wise direction.
d. Quadrant of Zone Method – the area to be searched is divided into four quadrants
and each searcher is assigned to one quadrant.
e. Wheel, Radial or Spoke Method – is applicable for area which is considered to be
approximately circular or oval. The area is then divided into six quadrants in a pie-
like fashion.
E. Notes Taking
Note taking must be a constant activity throughout the processing of the crime
scene.Notes must include:
a. Detailed written description of the Crime Scene with locations of recovered physical
evidence;
b. The time when the physical evidence was discovered;
c. The person who discovered and collected the physical evidence;
d. The time when evidence was packaged and marked; and
e. The disposition of the item when it was collected.
F. Collection of Physical Evidence
The competence to recognize and properly collect physical evidence is critical to both
solving and prosecuting crimes.

12. The team leader is always informed of significant evidence located. The evidence
collectors shall put his initial, location and date of collection on the item and turn it over to the
evidence custodian for documentation and safekeeping.
PHYSICAL EVIDENCE – these are the articles and materials which are found in connection
with the investigation and which aid in establishing the identity of the perpetrator or the
circumstances under which the crime was committed or which, in general assist in the
prosecution of criminal. It embraces any object, living or inanimate, solid, liquid, or gas state.
What are the procedures needed for the care of physical evidence?
In order to introduce physical evidence in court, three important factors must be
considered:
a. The article must be properly identified
b. Chain of custody must be proved
c. The evidence must be material and relevant
CHAIN OF CUSTODY
It is the number of persons who handled and possessed the pieces of evidence the
moment they were collected, marked and tagged, up to the time of the final disposition of the
case.
G. Conduct of Final Survey
The team leader makes a final review on the crime scene to determine whether or not
the processing has been completed.
H. Release of the Crime Scene
The release of the crime scene is done if the investigator is satisfied that all pieces of
evidence have been recovered. Thus, the investigator must evaluate the items recovered from
the results of the interrogations of the suspect/s and the interview of the witnesses. He must
bear in mind that upon the formal release of the crime scene to the proper authority, the warrant
is already required for his re-entry to the crime scene.