Forensic Science
is the scientific discipline which is engaged to the recognition,
identification, individualization and
evaluation of physical evidence by using the laws and principles
of natural science for the purpose of
administration to terminate doubtful questions in the court of law.
The term “forensics” taken from latin word “forensis”
which mean ‘the forum’. Forensic scientist also
play an active role in civil proceedings
(such as violate of agreement and negligence) and in regulatory
issues.
The principles of forensic science have a straight impact on criminal
proceedings.
Laws and Principles of Forensic Science -
Law of Individuality
Law of Progressive change
Principle of Comparison
Principle of Analysis
Principle of Exchange (Locard’s principle of Exchange)
Law of Probability
Law of Circumstantial facts.
1) Law of Individuality -
This law states that, “Every object whether natural or
man-made has a distinctive quality or characteristic in it which is not
duplicated in any other object,” in other words, no two things in this universe
are alike. Most common example is the human fingerprints; they are unique,
permanent and prove individuality of a person. Even the twins did not have the
same fingerprints.
Consider grains of sand, salt, seeds or man-made objects
such as currency notes, laptop, typewriter, etc. they may look similar but a
unique characteristic is always present between them.
This principle considered as the most basic elementary unit
of Forensic Science. Fingerprints, footprints, tool marks, obtained from the
crime scene are studied and analyzed on the principle of individuality.
2) Law of Progressive Change
This principle emphasizes that, “Everything changes with the
passage of time and nothing remains constant. “ The changing frequency varies
from sample to sample and on different objects.
The crime scene must be secured in time otherwise a change
in weather (rain, heat, wind), presence of animals/humans, etc. affects the
crime scene. For example, a road accident on a busy highway may lose all essential
evidence if not properly secured on time.
A bullet fragments may grow rust, firearm barrels loosen,
shoes suffer wear and tear marks, wooden objects may suffer due to presence of
termite, etc. Longer the delay, greater the changes.
When samples are not much durable, several complications
occur in an investigation as the process of identification is affected due to
the variations in the main features of identification. Without an appropriate
preservative, tissue samples start degrading immediately and they need
immediate analysis.
The criminals undergo progressive changes with time. If he
is not apprehended in time he becomes
unrecognizable except his fingerprints or other characteristics of permanent
nature.
3) Locard’s principle of Exchange (Law of exchange)
This principle was stated by French scientist -Edmond Locard
(a pioneer in criminology and forensic science). Law of exchange states that, “As
soon as two things come in connection with each other, they mutually interchange
the traces between them.”
Whenever criminal or his weapon/instrument made connection with
the victim or the things surrounding him he left some traces at crime scene and
also picked up the traces from the area or person he has been in contacted with
(mutual exchange of matter). These traces are very helpful for investigation
purposes as these traces are identified by the expert and linked to its
original source resulted in the decisive linkage of the criminal with the crime
scene and the victim. This law forms the basis of scientific crime investigation.
This principle is validated in all cases where there is a
contact such as fingerprints, tyre marks, bullet residues, foot marks, hair
sample, skin, muscles, bodily fluids, blood, pieces of clothing etc. DNA
analysis is a straight application of this principle, where any such items are
under analysis which was believed to be held by the perpetrator.
Basic requirement of this law is the correct location of the
physical evidence -
i) What are the areas and things with which the perpetrator
or tool actually came in contact during the crime?
ii) Investigating officer should establish the correct
points of contact, its lead the investigation in correct direction.
4) Principle of Comparison – For laboratory Investigation
this law is very important. The law state that “Only the likes can be compared”.
It highlights the requirement of providing like samples and specimens for evaluation
with the questioned items’.
For example, if the murder is done by a firearm weapon then
it is useless to send a knife for comparison.
So, the important condition of this principle is to supply specimen/samples of like nature for proper assessment with the questioned sample discovered from the crime scene.
5) Principle of Analysis
This principle states that, “The quality of any analysis
would be better by collection of correct sample and its correct preservation in
the prescribed manner”. This leads to better result and avoid tampering,
contamination and destruction of a sample.
If you collect a hard disk in a paper bag, it can be damaged
when it falls within the range of a strong electromagnetic field resulted in
poor results. Hence, always appropriate and effective collection and packaging
techniques must be used.
6) Law of Probability
This law states that, “All identifications (definite or
indefinite), made consciously or unconsciously on the basis of probability.”
The perpetrator blood group is also the blood group of
various people is high, but the probability of the same occurring in the case
is low.
A woman with a tattoo bear on its right hand and an old injury
mark on head is reported missing, an unknown woman is found murdered with these
characteristics then the probability for cops that the unknown corpse is of
that missing woman is high. The probability that the dead body is of another
woman will be 1 in millions.
7) Law of Circumstantial facts
According to this law, “Facts cannot be wrong, they cannot
lie not wholly absent but men can and do.” This law emphasizes the significance
of circumstantial facts and supports that a statement given by a human may or
may not be accurate. In an investigation identified and discovered facts are
more accurate and reliable than any eyewitness.
Conclusion
Forensic science by these principles is used for recognition, identification; individualization of pieces of evidence collected from the scene of crime and guides the criminal proceedings from the discovery of a crime to the conviction of the accused, helping the process of investigation.
MR. DEEPAK PAWAR has been working as Finger Print Expert / Police Officer in Finger Print Bureau , Delhi Police at New Delhi since 2001 . He is the senior most Finger Print Expert , attending / visited several scene of crime and solved many crime cases .He has passed M.Sc (Chemistry) and he is the Member of International Association of Identification . He is the Member of Delhi Police welfare association . He is supervising the Forensic , New Delhi District , Mobile Crime Team . He is one of the Expert in the Special Investigation Team held for investigation of important cases . He has been giving fingerprint proficient training to Delhi Police personnel's . He has been Presented / giving lectures on topics related to forensic science . He is also making examination paper of Finger Print proficient course . He is awarded with Police Medal by MHA and Delhi Police.