Forensic Science: Evidentiary Value & Real vs. Reel Life

Forensic Science is the use of scientific principles, theories and experiments to help investigate a civil or criminal case. Forensic Science, in this era of science and technology, has developed in such a way that crime investigations now heavily depend on it. Forensic Science, in criminal cases, is mainly related to the collection, preservation, identification, recognition, individualization and evaluation of the physical evidence obtained throughout the criminal investigation starting from the crime scene itself. Most of the countries in world have established and authorized the use of forensic science to examine the physical evidence as it is one the prime sector which plays a significant role for the administration of criminal justice.

History and Development

The history of forensic science dates back to 44 B.C. when a Roman physician, Antistius, performed the first officially recorded autopsy on the slain body of Roman politician, Julius Ceaser. In 1248, forensic science hit a milestone when a director of justice, jail and supervision Mr. Song Ci introduced some traditional methods of calculating the time of death, protecting the evidences and finding out the cause of death. Slowly the development of forensic science began throughout the world. In 16th Century, two Italian surgeons, Fortunato Fidelis and Paolo Zacchia, laid the foundation of modern pathology by studying changes that occurred in the structure of the body as the result of disease.[1] Some even consider Paolo Zacchia as the “Father of Forensic Medicine and Social Hygiene.”[2]

During the period between 17th to 19th Centuries, the intellectual and philosophical movement had dominated the world of ideas in Europe. In this Age of Reason, the use forensic science in crime investigations lead to breakthrough in many cases and help prevent miscarriage of justice by convicting the actual criminal.

The conviction of John Toms and the trial and conviction of Warwick in 1816, both for murders, were two of such landmark cases which depicts the successful development of forensic science in crime investigation and attainment of criminal justice.

Now, in the 21st Century, forensic science has been the heart of any crime investigation. With the emergence and development in Forensic Ballistics, Toxicology, Optometry, Podiatry, Anthropometry, Pathology and and many more other sectors, the field of forensic science has emerged as a prominent contributor in the criminal justice system.

Locard’s Exchange Principle

The name of Dr. Edmond Locard (1877–1966) deserves a special mention in the development of modern forensic science. This “Sherlock Holmes of France” formulated a fundamental and basic principle of forensic science as “Everything and Everyone that enters a crime scene leaves some piece of evidence behind.” This is popularly known as Locard’s Exchange Principle.

Road to becoming a Forensic Expert

To become a Forensic Doctor, one requires a Bachelor’s degree along with Doctor of Medicine (M.D.) and a lot of experience. In India, to become a Forensic Doctor, one must complete his/her MBBS and join MD Forensic Medicine in a government or private hospital. After working for several years and having good knowledge of dead bodies, one can crack the entrance and qualify for the designation of Forensic Expert. Similarly for other units like fingerprint, ballistics, DNA profiling, polygraph etc. a person must have degree in Forensic Science, receive specialized trainings on those sectors and shall have work experience on same field.

Evidentiary value of Forensic Expert

Judges in the court do not always understand the evidence presented in the court. Due to this, every country in every legal system has provided for an expert witness who can help the judge by discussing the complex evidence presented in court. However, all the people working a filed cannot be regarded as expert. There are certain thresholds which one must pass, in order to be accepted as an expert. An expert is a person who has immense knowledge on a particular field of work along with lots of education, techniques, skills and work experiences.

An expert witness is one who, is capable of deducing opinions from knowledge, skill and experience or from the facts observed by him or noticed by others.[3] The testimony of forensic experts will play a significant role in any criminal case for both, prosecutor and defense.

Similarly, the Indian Evidence Act enumerates the Expert Opinion under Section 45. The aforementioned section allows the testimony of forensic experts as evidence. The Supreme Court in the case of State of Himachal Pradesh v. Jai Lal and Ors[4] explained that in order to bring the evidence of a witness as that of an expert it has to be shown that he has made a special study of the subject or acquired a special experience therein or in other words that he is skilled and has adequate knowledge of the subject.

In case of Saqlain Ahmad v. Emperor[5], the Allahabad Court stated that the opinion of expert cannot be the base of conviction unless it is corroborated by other evidence. So, until and unless the opinion of expert is in accordance with some other evidence, the testimony of expert carries no evidentiary value.

Reel vs Real life Forensic Techniques

Real life forensic techniques is far more complex and time consuming than those shown in movies or serials in reel life. In movies we have seen the use of forensics to gather evidence, but is that the real way? Below we shall discuss on some real life vs reel life scenarios.

  • Let us consider the scene of gathering finger prints. Gathering finger prints on crime scene is one prima facie task that every investigator undertakes. We have seen in movies or serials that forensic doctors simply put some kind of powder on surfaces that is likely to have finger prints and safely retrieve it. However, it is not that easy. There are various ways and techniques to recover and gather fingerprints from various surfaces using different chemicals and methods.
  • On Smooth Surfaces like glass which is smooth and non-porous, lifting fingerprints is easy as shown in movies or series. The forensics use titanium dioxide powder and apply it on surface with help of oblique light. After dusting, there appears the prints and they stick a tape onto it and send for analysis.
  • If the surface is curved or textured, this technique is of no use now. The experts use Mikrosil or silicone casting and make a replica of fingerprints from the surface to the silicone.
  • Fingerprints are 98% water, so if the fingerprint is exposed to water or wetness, its just 2% remaining. In such case, the suspended solution of molybdenum disulfide is used which reacts with the 2% of remaining fingerprints and helps in lifting the fingerprint safely.
  • In a murder crime scene there is a high chance that bloody fingerprints may be found. In such situations, the forensic team uses the mixture of Leucocrystal Violet with Hydrogen Peroxide which will react with blood and turn the bloody fingerprint into violet color making it perfectly visible and easy to gather.
  • Another scene is of identifying blood stains. In reel life we have seen that the investigators use a spray like chemical to see a change in color and detect the traces of blood. But in real life that does not happen. The forensics use two different types of chemicals and conduct a Kastle-Meyer test. First they add phenolphthalein to the swab and then add couple of drops of hydrogen peroxide. If there are traces of blood on the sample, the two compounds will react and turn the phenolphthalein pinkish in color. This way, a sample or swab is tested to have blood stains or not.


There is a thing in common between a crime scene analyst, forensic doctor, fingerprint expert or DNA analyst and that is, they all use science and scientific measures to help solve a criminal case. With the advancement in science and technology, there has been a significant rise in crime rates and more advanced ways of committing crime. In such situation, the field of forensics carries a significant and prominent role to help attain justice by punishing the criminals. The forensic experts are regarded as a crucial witness who help determine the path of trial. These experts need a lot of education, knowledge, skills and work experience to be regarded as Forensic Expert and the methods they use in investigation is more complex, hard and time consuming than those shown in movies or serials or TV shows.

[1] Patricia E. Suter, Russell D. Earnest, Corinne P. Earnest, “The Hanging of Susanna Cox: The True Story of Pennsylvania’s Most Notorious Infanticide and the Legend that Kept it Alive“, (2010).

[2] Ibid 1.

[3] J.B. Mukerjee, “Forensic Medicine and Toxicology“, 4th Edition (2011).

[4] (1999) 7 SCC 280.

[5] AIR 1936 All 165.

Ashutosh Pandey from National Law College, Nepal

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