The role of an expert witness rendering opinion evidence before the Court may be explained by referring to the following observations of this Court in Ramesh Chandra Agrawal v. Regency Hospital Limited & Ors., (2009) 9 SCC 709:
“16. The law of evidence is designed to ensure that the court considers only that evidence which will enable it to reach a reliable conclusion. The first and foremost requirement for expert evidence to be admissible is that it is necessary to hear the expert evidence. The test is that the matter is outside the knowledge and experience of the layperson. Thus, there is a need to hear an expert opinion where there is a medical issue to be settled. The scientific question involved is assumed to be not within the court’s knowledge. Thus cases where the science involved, is highly specialized and perhaps even esoteric, the central role of an expert cannot be disputed…”
Undoubtedly, it is the duty of an expert witness to assist the Court effectively by furnishing it with the relevant report based on his expertise along with his reasons, so that the Court may form its independent judgment by assessing such materials and reasons furnished by the expert for coming to an appropriate conclusion. Be 38 that as it may, it cannot be forgotten that opinion evidence is advisory in nature, and the Court is not bound by the evidence of the experts. (See The State (Delhi Adminstration) v. Pali Ram, (1979) 2 SCC 158; State of H.P. v. Jai Lal & Ors., (1999) 7 SCC 280; Baso Prasad & Ors. v. State of Bihar, (2006) 13 SCC 65; Ramesh Chandra Agrawal v. Regency Hospital Ltd. & Ors. (supra); Malay Kumar Ganguly v. Dr. Sukumar Mukherjee & Ors., (2010) 2 SCC (Cri) 299).
Like all other opinion evidence, the probative value accorded to DNA evidence also varies from case to case, depending on facts and circumstances and the weight accorded to other evidence on record, whether contrary or corroborative. This is all the more important to remember, given that even though the accuracy of DNA evidence may be increasing with the advancement of science and technology with every passing day, thereby making it more and more reliable, we have not yet reached a juncture where it may be said to be infallible. Thus, it cannot be said that the absence of DNA evidence would lead to an adverse inference against a party, especially in the 39 presence of other cogent and reliable evidence on record in favour of such party.
This leads us to the question of the propriety of relying upon the superimposition test conducted in the instant case for identifying the deceased. As noted supra, the learned counsel for the appellants has argued that evidence pertaining to the use of the superimposition technique is not a tangible piece of evidence. We find ourselves unable to agree with this view. There cannot be any dispute that evidence on superimposition is also based on experts’ opinion. We would like to note that the use of the superimposition technique in Indian investigations for identification purposes is not a new phenomenon. Notably, it has been employed in the investigations pertaining to the Nithari murders, the Russian murder incident in Goa in 2008, and even before that in the Morni Hill murder case and the Paharganj bomb blast case as far back as in 1996, and the Udhampur murder case in 2005 (See Modi, A Textbook of Medical Jurisprudence and Toxicology, 26th edn., 2018, pp. 267271).
This Court itself has placed reliance on the identification of the deceased through superimposition on several occasions (see 40 Shankar & Ors. v. State of Tamil Nadu, (1994) 4 SCC 478; Swamy Shraddananda v. State of Karnataka, (2007) 12 SCC 288; Inspector of Police, Tamil Nadu v. John David, (2011) 5 SCC 509; Mahesh Dhanaji Shinde v. State of Maharashtra, (2014) 4 SCC 292), clearly indicating that it is an acceptable piece of opinion evidence.
It is relevant to note that all of the decisions of this Court cited in the above paragraph were based on circumstantial evidence, involving aspects such as the last seen circumstance, motive, recovery of personal belongings of the deceased, and so on, and therefore in none of the cases was the superimposition technique the sole incriminating factor relied upon to reach a conclusion of guilt of the accused. Indeed, in Mahesh Dhanaji Shinde (supra), the Court also had the advantage of referring to a DNA test, and in John David (supra), of referring to a DNA test as well as a dental examination of the deceased, to determine the identity of the victim. This is in line with the settled practice of the Courts, which generally do not rely upon opinion evidence as the sole incriminating circumstance, given its fallibility. This is particularly true for the superimposition technique, which cannot be regarded as infallible.