CRIMINALISTICS (B.Sc.- FS 303)
UNIT 2: CRIME SCENE EVIDENCE
Crime Scene: A crime scene is any location where a crime has occurred or where evidence of a
crime may be found.
Crime Scene Evidence: Evidence can be anything from fingerprints, blood, and DNA to
weapons, documents, and even the positions of objects at the scene.
CLASSIFICATION OF EVIDENCES
Physical evidence: Physical evidence is any object that can establish that a crime has been
committed or can provide a link between a crime and its victim or between a crime and its
perpetrator. In other words, physical evidence can be anything from massive objects to microscopic
items, generated as part of a crime and recovered at the scene or at related locations. Physical
evidence, when it is recognised and properly handled, offers the best prospect for providing
objective and reliable information about the incident under investigation. The role of forensic
science services starts at the crime scene with the recognition and recovery of physical evidence. It
proceeds with its analysis and the evaluation of the results in a laboratory, and the presentation of
the findings to judges, prosecutors, lawyers and others in need of the factual information.
Examples Of Physical Evidence
Blood Stains Flammable Liquids
Seminal Stains Firearms Evidence
Hair Questioned Documents
Fibres and Threads Narcotics, Controlled Substances and Medicinal Preparations
Glass Impression evidence – shoe prints, tire tracks or tool marks
Paint / Paint Chips Biological material - blood, semen or saliva
Accelerants Soil and vegetation
Tool Marks Latent Fingerprints
Examination Of Physical Evidence: The examination of physical evidence by a forensic
investigator is usually undertaken for identification and comparison. The purpose of identification
is to determine the physical or chemical identity of a substance with as near absolute certainty as
existing analytical techniques will permit. The objective of a comparison is to determine whether
or not the suspect specimen and a control specimen have a common origin, by subjecting them to
the same examinations and tests. In a comparison analysis, the forensic investigator must not forget
the role that probability plays a determining factor in the discovering the origins of two or more
specimens. Evidence is said to possess individual characteristics when it can be associated with a
common source with extremely high degree of probability. However, evidence that can be
associated only with a group and never with a single source is said to possess class characteristics.
,The Role Of Physical Evidence
1) The physical evidence left behind at a crime scene plays a crucial role in reconstructing the
events that took place surrounding the crime. Reconstruction is a team effort that involves
putting together many different pieces of a puzzle.
2) Although the evidence alone does not describe everything that happened, it can support or
contradict accounts given by witnesses and/or suspects.
3) Information obtained from physical evidence can also generate leads and confirm the
reconstruction of a crime to a jury.
4) The collection and documentation of physical evidence is the foundation of a
reconstruction.
5) The right connections have to be made among all the parts involved so as to portray the
relationship among the victim, the suspect, and the crime scene. If successful,
reconstruction can play a vital role in aiding a jury to arrive at an appropriate verdict.
6) Physical evidence can prove a crime has been committed or establish key elements of an
offence. Example: In cases of alleged rape, the victim‘s torn clothing and injuries may be
sufficient to prove non-consent.
7) Physical evidence can place the suspect in contact with the victim or with the crime scene.
Example: Victims hair caught in the suspect‘s watch band.
8) Physical evidence can establish the identity of persons connected to the crime. Example:
Fingerprints developed within the crime scene and subsequently identified to a person.
9) Physical evidence can exonerate/ exclude the innocent. Example: In cases of alleged rape
DNA analysis of samples taken from a victim may clear a suspect.
10) Physical evidence can corroborate the victim‘s testimony. Example: In cases of alleged
assault, minor injuries to a suspect‘s knuckles may corroborate a victim‘s claim that he
was punched in the mouth. A suspect confronted with physical evidence may make
admissions. Example: Stolen property found in the suspect‘s possession.
11) Physical evidence is more reliable than eye witnesses. Observations made during violent
or stressful situations have often proved to be inaccurate.
TRACE EVIDENCE
Trace evidence refers to a sub-part or component of a material, or small, often microscopic amounts
of material not readily visible to the naked eye. Trace evidence is usually transferred through
physical contact during the commission of a crime or occurrence of an incident. In simple words,
trace evidence often refers to minute samples of a substance, particularly fibres, hairs, glass
fragments and paint chips. Crime scenes will commonly contain trace evidence, often caused by the
perpetrator unconsciously coming into contact with surfaces and leaving behind or picking up
particulates. The presence of trace evidence is particularly dependent on its persistence, as some
, particles and substances will remain on a surface more readily and for a longer period of time than
others. The extent to which evidence will persist depends on the size and shape of the particle, the
amount deposited, activity between deposition and recovery, the nature of the environment, and the
amount of time passed. Small particles will persist for longer than larger particles, as they are more
likely to become lodged in the surface material. Irregular surfaces, such as certain fabrics and wood,
will collect particulates more readily than smooth surfaces, as there may be minute crevices for
particles to adhere to. When trace evidence is found, numerous factors should be taken into
consideration. The regularity of a material is of great significance, as extremely common items may
not be particularly useful. It is trace evidence that is unusual or unique to a particular environment
or scene that will be of the greatest importance to an investigation. Some forms of trace evidence
may be especially unusual at a scene, giving them particular significance. It should be considered
that the lack of trace evidence may either indicate extensive cleaning by the perpetrator or that the
event did not occur at that location. Various methods are employed in the collection of trace
evidence, the method used depending on the type and nature of evidence. Larger items, such as long
fibres, may be collected by hand or tweezers. One of the simplest methods of recovery is to shake
the item over a sheet of paper or container. However, this does not allow for the exact location of
evidence on the item to be documented. Some particles will not be dislodged by shaking the item,
therefore brushing the item may be necessary. A common method of trace evidence collection is the
taping technique, particularly beneficial in the case of fibres and hairs. A strip of clear adhesive tape
is applied to the surface, peeled off, and placed against backing card. This allows a note to be made
of the exact location of the trace evidence. Vacuum lifting is a particularly useful method of trace
collection. The scene is divided into smaller grids for the purpose of ease and documentation. The
vacuum is used in each grid with a different filter every time. Each individual filter can then be
packaged and analysed separately, allowing for the exact grid location of items of evidence to be
noted. This method is not as precise as adhesive taping, but it is ideal for collecting particulates.
Practically every crime/incident involves trace evidence in one form or other. Additionally, transfer
of trace evidence is often not obvious to the persons involved in the crime. Hence, trace evidence is
unlikely to be completely absent for any case. The limiting factor would be human failure to find it,
understand and interpret it in relation to the crime scene where it was discovered. The significance
of the evidence depends on several factors, such as the uniqueness of the evidence and the number
of associations established for different types of evidence.
Trace Evidence services Include:
- Explosives analysis Fibre - Fibre examination
- Glass examination - Ignitable liquid residue analysis Paint examination
- Soil examination - Gunshot residue (GSR) analysis
UNIT 2: CRIME SCENE EVIDENCE
Crime Scene: A crime scene is any location where a crime has occurred or where evidence of a
crime may be found.
Crime Scene Evidence: Evidence can be anything from fingerprints, blood, and DNA to
weapons, documents, and even the positions of objects at the scene.
CLASSIFICATION OF EVIDENCES
Physical evidence: Physical evidence is any object that can establish that a crime has been
committed or can provide a link between a crime and its victim or between a crime and its
perpetrator. In other words, physical evidence can be anything from massive objects to microscopic
items, generated as part of a crime and recovered at the scene or at related locations. Physical
evidence, when it is recognised and properly handled, offers the best prospect for providing
objective and reliable information about the incident under investigation. The role of forensic
science services starts at the crime scene with the recognition and recovery of physical evidence. It
proceeds with its analysis and the evaluation of the results in a laboratory, and the presentation of
the findings to judges, prosecutors, lawyers and others in need of the factual information.
Examples Of Physical Evidence
Blood Stains Flammable Liquids
Seminal Stains Firearms Evidence
Hair Questioned Documents
Fibres and Threads Narcotics, Controlled Substances and Medicinal Preparations
Glass Impression evidence – shoe prints, tire tracks or tool marks
Paint / Paint Chips Biological material - blood, semen or saliva
Accelerants Soil and vegetation
Tool Marks Latent Fingerprints
Examination Of Physical Evidence: The examination of physical evidence by a forensic
investigator is usually undertaken for identification and comparison. The purpose of identification
is to determine the physical or chemical identity of a substance with as near absolute certainty as
existing analytical techniques will permit. The objective of a comparison is to determine whether
or not the suspect specimen and a control specimen have a common origin, by subjecting them to
the same examinations and tests. In a comparison analysis, the forensic investigator must not forget
the role that probability plays a determining factor in the discovering the origins of two or more
specimens. Evidence is said to possess individual characteristics when it can be associated with a
common source with extremely high degree of probability. However, evidence that can be
associated only with a group and never with a single source is said to possess class characteristics.
,The Role Of Physical Evidence
1) The physical evidence left behind at a crime scene plays a crucial role in reconstructing the
events that took place surrounding the crime. Reconstruction is a team effort that involves
putting together many different pieces of a puzzle.
2) Although the evidence alone does not describe everything that happened, it can support or
contradict accounts given by witnesses and/or suspects.
3) Information obtained from physical evidence can also generate leads and confirm the
reconstruction of a crime to a jury.
4) The collection and documentation of physical evidence is the foundation of a
reconstruction.
5) The right connections have to be made among all the parts involved so as to portray the
relationship among the victim, the suspect, and the crime scene. If successful,
reconstruction can play a vital role in aiding a jury to arrive at an appropriate verdict.
6) Physical evidence can prove a crime has been committed or establish key elements of an
offence. Example: In cases of alleged rape, the victim‘s torn clothing and injuries may be
sufficient to prove non-consent.
7) Physical evidence can place the suspect in contact with the victim or with the crime scene.
Example: Victims hair caught in the suspect‘s watch band.
8) Physical evidence can establish the identity of persons connected to the crime. Example:
Fingerprints developed within the crime scene and subsequently identified to a person.
9) Physical evidence can exonerate/ exclude the innocent. Example: In cases of alleged rape
DNA analysis of samples taken from a victim may clear a suspect.
10) Physical evidence can corroborate the victim‘s testimony. Example: In cases of alleged
assault, minor injuries to a suspect‘s knuckles may corroborate a victim‘s claim that he
was punched in the mouth. A suspect confronted with physical evidence may make
admissions. Example: Stolen property found in the suspect‘s possession.
11) Physical evidence is more reliable than eye witnesses. Observations made during violent
or stressful situations have often proved to be inaccurate.
TRACE EVIDENCE
Trace evidence refers to a sub-part or component of a material, or small, often microscopic amounts
of material not readily visible to the naked eye. Trace evidence is usually transferred through
physical contact during the commission of a crime or occurrence of an incident. In simple words,
trace evidence often refers to minute samples of a substance, particularly fibres, hairs, glass
fragments and paint chips. Crime scenes will commonly contain trace evidence, often caused by the
perpetrator unconsciously coming into contact with surfaces and leaving behind or picking up
particulates. The presence of trace evidence is particularly dependent on its persistence, as some
, particles and substances will remain on a surface more readily and for a longer period of time than
others. The extent to which evidence will persist depends on the size and shape of the particle, the
amount deposited, activity between deposition and recovery, the nature of the environment, and the
amount of time passed. Small particles will persist for longer than larger particles, as they are more
likely to become lodged in the surface material. Irregular surfaces, such as certain fabrics and wood,
will collect particulates more readily than smooth surfaces, as there may be minute crevices for
particles to adhere to. When trace evidence is found, numerous factors should be taken into
consideration. The regularity of a material is of great significance, as extremely common items may
not be particularly useful. It is trace evidence that is unusual or unique to a particular environment
or scene that will be of the greatest importance to an investigation. Some forms of trace evidence
may be especially unusual at a scene, giving them particular significance. It should be considered
that the lack of trace evidence may either indicate extensive cleaning by the perpetrator or that the
event did not occur at that location. Various methods are employed in the collection of trace
evidence, the method used depending on the type and nature of evidence. Larger items, such as long
fibres, may be collected by hand or tweezers. One of the simplest methods of recovery is to shake
the item over a sheet of paper or container. However, this does not allow for the exact location of
evidence on the item to be documented. Some particles will not be dislodged by shaking the item,
therefore brushing the item may be necessary. A common method of trace evidence collection is the
taping technique, particularly beneficial in the case of fibres and hairs. A strip of clear adhesive tape
is applied to the surface, peeled off, and placed against backing card. This allows a note to be made
of the exact location of the trace evidence. Vacuum lifting is a particularly useful method of trace
collection. The scene is divided into smaller grids for the purpose of ease and documentation. The
vacuum is used in each grid with a different filter every time. Each individual filter can then be
packaged and analysed separately, allowing for the exact grid location of items of evidence to be
noted. This method is not as precise as adhesive taping, but it is ideal for collecting particulates.
Practically every crime/incident involves trace evidence in one form or other. Additionally, transfer
of trace evidence is often not obvious to the persons involved in the crime. Hence, trace evidence is
unlikely to be completely absent for any case. The limiting factor would be human failure to find it,
understand and interpret it in relation to the crime scene where it was discovered. The significance
of the evidence depends on several factors, such as the uniqueness of the evidence and the number
of associations established for different types of evidence.
Trace Evidence services Include:
- Explosives analysis Fibre - Fibre examination
- Glass examination - Ignitable liquid residue analysis Paint examination
- Soil examination - Gunshot residue (GSR) analysis
