Forensic Science – Notes


Definition and Meaning of Forensic Science: Forensic has been derived from a Latin term ‘Forensis’ which means meeting place where a person sits collectively and discuss crime. Forensic Science is that branch of science which deals with all the branches of science collectively in order to solve the problem of law and justice.
Forensic Science can also be defined as a scientific discipline which is directed to the recognition, identification and evaluation of physical evidence by application of principles of forensic science for the administration of criminal justice.

Cui Bono/Qui Bono:
• Who is interested?
• Who is benefited?

Scene of Crime:
Some of the crime is the meeting place of the culprit and accused or a place where crime has been committed.
It is the starting point for the investigator, which provides him with information on the victim and the suspect to reconstruct the crime.
Importance of Scene Crime:-
1. Identification of Culprit and victim (corpus deliciti).
2. Whether the death is murder, accident or suicide especially in case of unnatural death.
3. Manner of death or manner of offence.
4. Types of injuries or wounds.
5. Time since death or time since injury.
6. Pattern (sequence) of crime.
7. The number of culprits or victims.
8. Weapon used.
9. Collection of all pieces of evidence.

Types of Scene of Crime:
• Indoor: Inside any building or house.
• Outdoor: In an open place.
• Partially indoor or outdoor: For instance, “A” was murdered inside the house, but he died after coming out of the house.

Evaluation in Forensic Science:
1. Protection
2. Photography
3. Sketching
4. Searching

  • Zonal method
  • Spiral method
  • Stripped method
  • Wheel method
  • Crosshatched method

5. Handling Clues
6. Recording
7. Modern Aids

1. Protection: As soon as a possible, proper authority should reach ‘Scene of Crime’. As the scene of the crime is not permanent certain steps need to be followed:

  • Step 1. If the person is injured, then do get him into the hospital to save his life.
  • Step 2. Don’t give permission to relatives or friends to enter into the scene of the crime.
  • Step 3. Doctors, draftsman, photographers and FSL should reach as soon as possible.
  • Step 4. If culprit found at the scene of the crime, then he should be arrested immediately. If suspected then he should be detained.
  • Step 5. Culprit and witness should not allow communicating. Eye witness should be kept secret.
  • Step 6. If the scene of the crime is outdoor, then a large area should be covered and put a barricade around it.
  • Step 7. Preserve and send evidence as soon as possible.

2. Photography:

  • It is permanent in nature
  • The recollection of memory of witnesses.
  • Injuries and wounds should be photographed which help judge to know the gravity and seriousness of the crime.
  • Officer-in-charge has so much burden, he is not able to concentrate, it maybe he is not able to collect proper evidence which can be seen in the photographs.

3. Sketching: It means making sketch including all measurements which is not possible on photographs, by using symbols.
4. Searching: There are various methods for searching for clues at the scene of the crime:

  • Zonal Method: The entire area to be searched is blocked into a big square which is subdivided into small squares.
  • Spiral Method: Searchers move along the path of the spiral until they reach the centre of the scene of the crime. They cover the entire area so that no physical evidence left.
  • Stripped Method: Scene of crime is divided into strips for searching for clues.
  • Wheel Method: The entire scene of the crime is marked as a circle. They repeat the process several times.
  • Cross Hatched Method: It is two-dimensional searching in which two methods have been used.

5. Handling Clues: Clues should be handled in a proper manner with care.

  • Eg. Hair kept in a paper, bloodstain should be kept in dry polythene. If any explosive material is found special care should be taken. It is very difficult to reserve micro evidence.

6. Recording: When police reach the scene of the crime, a report is to be prepared. The thing which should be mentioned are:

  • Body Fluid- (blood, saliva, sweat, etc.).
  • Corpse- intact or mutilated.
  • Documents- any suicidal note or paper.
  • Fibres:
    • Natural:- Plant Originating (Cotton) and Animal Originating.
    • Artificial:- Manmade like polythene, cloth, etc.
  • A firearm- revolver, needle, gun, etc.
  • Explosives- RDX etc.

7. Modern Aids: It includes the following:

  • Investing kit:-
    • Searching material:
      • Torch of high voltage.
      • Magnifying glass etc.
    • Making and breaking material.
    • Blood testing material or body fluid testing material:
      • Chemicals
      • Cotton
      • Test tubes etc.
    • Lifting up material: POP for carrying footprints.
  • Experts:- Medical assistance, police officials, fingerprinting experts, photographers, etc.
  • Dog squads:- To trace the narcotics, to protect the scene of the crime, identify the criminals.
  • Flying squad.
  • Mobile Unit:- It is a van regarded as mini forensic science laboratory reach at the place of offence to collect evidence.

Discovery of physical trade evidence:

  • Evidence
  • Eye Witnesses Physical Evidences
  • Loophole- it might become hostile; become dead or loss memory. Taken from the scene of the crime. It is permanent and never changes.
  • Physical Evidence
  • Macro Micro
  • Seen from naked eyes. Cannot be seen from naked eyes.
    • E.g.- weapon, firearm, etc. E.g.- fibres, hair, dust, soil, etc.

Blood can come in the category of micro or macro-based upon the quantity.

Micro Evidence:
• Hair: It has a very important role in the investigation process. It varies from offence to offence.
• Location: Hair can be found with blood, tools, scene of crime etc.
• Principles governing hair as evidence: A- Locard’s Principle of Exchange, B- Principle of Individualisation.

Locard’s Principle of Exchange:
Wherever two bodies come in contact there is always a mutual exchange. Each and every offence is governed by the card principle of exchange.
Example- If a thief comes in the house, he carries some evidence like soil, so it is the mutual exchange between culprit and scene of the crime.

Principle of Individualisation:
Each and every entity is unique. Characteristics of every individual are different.
Example- fingerprints, DNA etc.

Kinds of Hair:
1. Medical Basis
2. Criminal Law:

• Incriminating Hairs- It is used to identify the culprit or victim. It may be of human beings or animals. It depends upon the nature of the offence. Location- blood or body fluid, cloths, tools, bedsheets, etc.
• Sample Hairs- To compare with incriminating hairs which have been received from the scene of the crime. It is used to know the number of persons involved.

Methods to collect Incriminating Hairs:

  1. If hairs are very long, then they can be collected by using hands.
  2. If the hairs are very short, then tools can be used.
  3. Hair collected by using adhesive tape. It is used to collect hair from an object. Example- hairs from any object like bedsheet or sofa. But with hairs, many other parties stick to adhesive tape, to separate them, Xylene solution is used.
  4. To cover a larger area, the vacuum cleaner can be used.

Methods to collect Sample Hairs:

  1. Brushing/Combing- A hard comb is used to get samples. Sample hairs are best representative hairs when combed.
  2. Pulling out- Best sample hairs can be taken by this method. But it is extremely painful in the case of a living person.
  3. Clipping out- Cut the hair from it has close contact with skin. But it is the least used method.
  4. Stretching- Pull the dry stains found at the scene of the crime.
  5. Dissolving- If the hair is attached with some other thing, then chemicals are used to separate them.

Medico-Legal Importance:

  1. It connects culprit, victim and scene of the crime.
  2. Ascertainment of time since death.
  3. Ascertainment of sec of victim or culprit.
  4. Ascertainment of the age of the person.
  5. Type of Offence: Example- if death is due to burning, the tip of hair becomes singed. If death is due to lightning, hair change like spring.
  6. DNA Testing: If roots and follicle of hair are present, then DNA can be traced out.
  7. To ascertain the race of a person.
  8. Type of weapon used: Example- if any sharp weapon is used then the tip of the hair is sharped. If the hair has been pulled then it will become like spring.

Article 20(3) of the Constitution of India:
No one can give a witness against himself. Previously, it was treated as unconstitutional if the police take sample hairs of a person without his permission. But the court held it constitutional as it is a part of the investigation process.

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