Evidence Management
THE LOCARD EXCHANGE – Dr. Edmond Locard: Every criminal can be connected to a crime by small particles carried from the scene.
Whenever 2 objects come in contact with one another, a cross-transfer of physical evidence can occur.
The intensity, duration, and nature of the materials in contact determine the extent of the transfer.
Physical Evidence: It never lies
Physical evidence consists of any and all objects that can be useful to prove or disprove a fact under investigation or to evaluate the pattern of events occurred at the time of commission of crime or simply saying any object that can connect a crime and its victim or a crime and its perpetrator. An investigator can effectively make use of the physical evidences only if he properly recognizes it at the scene.
As it is a crucial link to reach the criminal so it plays a very critical role in successfully solving the case? Therefore the approach towards physical evidence should be objective, systematic and thoughtful. They can tell a true story of the crime scene if they are properly managed and examined carefully. Physical clues initially though irrelevant may become crucial to successful resolution of the case.
Physical Evidence
- Physical evidence refers to any material items that would be present at the crime scene, on the victims, or found in a suspect’s possession.
- Type of evidence forensic scientists are most interested in
- Forensic scientists will…
– Observe physical evidence
– Determine identity
– Determine origin - Can be any material or object
- Take any form
– Large as a building
– Fleeting as an odor (smell or fragrance)
– Small as a hair
– Microscopic as DNA - Much more reliable than testimonial evidence
What will evidence collected at a scene do for the investigation?
- May prove that a crime has been committed
- Establish key elements of a crime
- Link a suspect with a crime scene or a victim
- Establish the identity of a victim or suspect
- Corroborate verbal witness testimony
- Exonerate the innocent.
- Give detectives leads to work with in the case
Common Types of Physical Evidence
| Drug and toxic substance | Resins, plastics | Fingerprints |
| Paints | Explosive residues | Hair |
| Gun shot residues (GSR) | Serial numbers | Tissues |
| Firearms and ammunition | Documents | Pollen |
| Impressions | Fibers | Wood material |
| Petroleum products | Soil | Feathers |
| Alcohols (esp. ethanol) | Glass | Bones |
| Rubber material | Blood and other body fluids | Tool marks |
- Trace evidence (gunshot residue, paint chips, broken glass, unknown chemicals, and drugs).
- Impressions (fingerprints, footprints, bite marks, tyre tracks and tool marks).
- Body fluids (blood, semen, saliva, vomit).
- Wood, soil and plants
- Petroleum products.
- Hair and fibers.
- Weapons and firearms evidence (knife, guns, swords, bullet holes, cartridge case).
- Bomb Fragments/explosives.
- Narcotics and poison residues.
- Powder residue (firearm discharge residues).
- Questioned documents (diaries, suicide note, phone books; also includes electronic documents like answering machines and caller ID units).
Types of Evidence
- Testimonial evidence includes oral or written statements given to police as well as court testimony by people who witnessed an event.
- Physical evidence refers to any material items that would be present at the crime scene, on the victims, or found in a suspect’s possession.
- Trace evidence refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or skin cells.
Three Major Types Of Evidence
- Direct Evidence
- Indirect Evidence
- Real Evidence
- DIRECT EVIDENCE
a. Evidence which is a fact all by itself.
b. It stands on its own two feet and without any other explanation, proves the point. - INDIRECT EVIDENCE
a. Also known as circumstantial evidence.
b. It is that evidence that, in itself, does not directly prove the fact in issue but establishes a certain fact or series of facts which tend to prove certain elements of the case or question. - REAL EVIDENCE
a. Sometimes called demonstrative evidence
b. Real evidence speaks for itself, except for identifying the object and establishing its connection with the crime, it tells its own story.
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Types of Physical Evidence
- Trace Evidence
- Transient evidence
- Conditional Evidence
- Indirect Evidence
- Circumstantial Evidence
- Individual evidence
- Class evidence
1. Trace Evidence
Trace evidence refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or skin cells.
2. Transient evidence
– Temporary evidence
– Can be easily changed or lost
– Usually observed by first officer on scene and must be recorded at that time
- Examples?
– Odors - Perfume, cigarette smoke, gas
– Temperature - Coffee pot, car hood, water in bath tub, dead body
– Imprints - Footprints in sand, fingerprints in dust, teeth marks in perishable food
3. Conditional Evidence
- Produced by a specific action or event at the scene
- Must be observed and recorded
- Examples
– Lights
– Garage door
– Doors
– Windows
– Position of body
– Position of furniture
4. Indirect Evidence
- Evidence that does not prove or disprove a fact in question
- Evidence providing only a basis for inference about a disputed fact
- May prove something like the possession of controlled substances or driving under the influence
5. Circumstantial Evidence
- Evidence based on suggestion rather than personal knowledge
- Implies a fact or event without actually proving it
- The more circumstantial evidence there is, the greater it weighs
- Probability and statistics important
- Examples
– Blonde hair found in hand of murder victim with black hair
– Size 10 sneaker print near the body
– Both of these limit the pool of suspects
6. Individual Evidence
- Material that can be related to a single source
- Individualization always involves a comparison
- Narrows an identity to a single person or thing
- Examples
– DNA
– Fingerprints
– Handwriting
– Some physical evidence - Piece of glass that fits another piece like a jigsaw puzzle
7. Class Evidence
- Material that can be associated with a group of items that share properties or characteristics
- Narrows an identity to group of persons or things
- Examples
– Blue jeans - We can use some individualization such as length, style, brand, shade, surface treatment but there are still thousands of jeans like that
Value of Physical Evidence
- Can prove crime has been committed
– Gasoline at a scene of a fire - Back up witness testimony or disprove it
– Test blood stains of suspects - Link suspect with victim or crime scene
– Broken glass of headlight in cuff of suspects pants at scene of hit and run - Determine identity of people associated with crime
– Fingerprints, DNA - Allow investigators to reconstruct a crime
– Blood spatter patterns
Collection and packing of evidences:
This is one of the most crucial steps in the investigation of the crime scene. Keeping in mind the evidential value of every physical evidence it should be handled and packed carefully and properly. If the evidence is altered or destroyed during the process making it inadmissible to the laboratory personnel and thus can’t aid in the further investigation of the case.
Hence it would be fruitful if the methodology for the collection & packing of the physical evidence is such that its integrity is maintained so that evidence collected are also retained in its original condition as obtained at the crime scene.
Collection and packing of the evidences differ depending on the type of evidence and the substrate upon which it is found. If the evidence is easily broken or can easily be lost, the entire object should be collected and packaged, if size and circumstances permit.
Each different item or similar items collected at different location must be placed in separate containers to avoid cross contamination.
Each item of evidence collected should be marked for identification by placing date, location, item and case number. Seal the container and it should be signed by the investigator.
Some commonly encountered evidences are collected and packed in following ways:-
- Blood stain if on large object, moistened the disinfected wash with distilled water and wash the stained area. Take wash from the area close the blood stain also, both clean should be air dried. Pack in the solid container, avoid plastic containers. If blood stain is on clothing, the stained area should be cut, air dried and packed in paper bags.
- Seminal Stains if wet the article should be air dried thoroughly, wrap the stained article in paper bags.
- Hair and fiber should be closely searched and whenever possible submit the article on which hair and fiber are found. If not possible individual fiber or hair should be picked with the help of tweezers and forceps and packed in separate envelops. Control samples for hair should include combed and pulled hairs from the head and pubic region. These hairs should be placed in a clean folded piece of paper or an envelope.
- Documents should be packed in plastic sheet protector, they should not be handled with bare hands, and care should be taken not to mark, alter or deface it.
- Glass particles should be collected properly and carefully with the help of forceps, place them in solid containers, and never use loose envelopes.
- For clothing and fabrics do not expose the wet item to excessive heat. Allow the wet item to air dry naturally by hanging it on a clean hanger or on a clean surface. The clothing should be packed in a clean paper bag, don’t use plastic bags.
- The articles containing the fingerprints and footprints must be touched as little as possible. Plastic impressions are usually photographed but may also be cast with a casting material to lift the impression. Latent fingerprint impressions require some sort of developing technique to be seen by the naked eye which are then lifted and photographed.
- Bite marks are found many times in sexual assaults and can be matched back to the individual who did the biting, for this they should be photographed with all necessary angles and view. If the bite mark has left an impression then may be a cast can be made of it.
- For paint fragments they should be collected in a paper packet and placed in an envelope.
Forwarding evidence to FSL:
After collection the packed should be properly sealed by the investigator and a sample of seal impression is also forwarded along with the exhibits to the laboratory by an authorized messenger. It should be accompanied by an authorized letter of the court requesting the laboratory for the examination of the exhibits. Control samples should also be sent along with the exhibits.
Continuity of possession or chain of custody must be established whenever evidence is presented in court as an exhibit. The court will require proof that evidence collected during an investigation and the evidence ultimately submitted to the court are one and the same. To prove that the integrity of the physical evidence has been maintained, a chain of custody must be maintained. This chain shows that who had contact with the evidence, at what time and under what circumstances.
Thus following types of information is needed to establish the chain of custody:-
- Name or initials of the individual collecting the evidence and each person subsequently having custody of it.
- Date when it was collected and transferred.
- Case number and type of crime.
- Victim’s name.
- Brief description of the item.
This information serves to prove the chain of custody to the court and assists in admitting the items into evidence.
Crime Scene Investigation | Forensic Science Notes Part-1
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