Law related to expert evidence is mentioned particularly in S.45 to S.51 of Indian Evidence Act and restricted to the interpretation of these sections only. The general rule is that the opinion of persons or the beliefs of the witnesses is not admissible in the Court.[1] However, in the course of time, the law related to expert evidence has been developed with the rapid development of technology and with the help of judicial decisions.

Witnesses are ordinarily to testify the facts in their direct knowledge leaving it to the judge to form opinions, inferences, or conclusions on the basis of such facts. Witnesses are ordinarily not to say what they thought or believed to be and therefore their opinions are irrelevant in a judicial inquiry but in certain special matters requiring special skill in the subject concerned, opinions of persons having special study, training, or experience are accepted as evidence.

In cross-examination, the lawyer may try to prove the incompetence of the expert by putting questions relating to his qualifications, training, and experience. Expert evidence is covered under s.45-51 of the Indian Evidence Act. S.45 of the Act allows that when the subject matter of inquiry related to science or art, as to require the course of the previous habit or study and in regard to which inexperienced persons are unlikely to form a correct judgment.

It allows an expert to tender evidence on a particular fact in question, and to show to the court that his findings are unbiased and scientific.S.46 of the Act states that facts, not otherwise relevant, are relevant if they support or are inconsistent with the opinion of experts when such opinions are relevant. S.47 of the Indian Evidence Act exclusively deals with the opinion as to the handwriting. The explanation further elaborates on the circumstances under which a person is said to have known the disputed handwriting. The expert opinion is not confined to handwriting alone. The opinions in relation to custo.ms are also admissible according to S. 48 of Indian Evidence Act.

Opinions of Experts: S.45, Indian Evidence Act, 1872

Principle:
Under Section 45, opinions of experts are relevant to questions of foreign law, science, art, identity, handwriting, or finger impressions. Expert testimony is admissible on the principle of necessity. The help of experts is necessary when the question involved is beyond the range of common experience or common knowledge or where the special study of a subject or special training or skill or special experience is called for. No man is omniscient; in fact, perfection is an attribute of divinity only.

As a general rule, the opinion of a judge, only plays a part and is thus relevant in the decision of a case, and therefore, the opinion of any person other than the judge about any issue or relevant fact is irrelevant in deciding the case. The reason behind such a rule is that if such opinion is made relevant, then that person would be invested with the character of a judge. Thus, Section 45 Is, therefore, an exception to this general rule, as it permits the experts' opinion to be relevant in deciding the case.

The reason behind this is that the The judge cannot be expected to be an expert in all the fields-especially where the subject matters involve technical knowledge[2] as he is not capable of drawing an inference from the facts which are highly technical. In these circumstances, he needs the help of an expert- who is supposed to have superior knowledge or experience in relation to the subject matter.

Scope:
“When the Court has to form an opinion upon a point of foreign law, or of science, or art, or as to identify handwriting or finger impressions, the opinions upon these points of persons specially skilled in such foreign law, science or art or in questions as to the identity of handwriting or finger impressions, are relevant Facts. Such persons are called experts.”

A Fact is something cognizable by the senses such as sight or hearing, whereas opinion involves a mental operation. Under Section 3, the opinion of a person will be a fact too. U/s 60 oral evidence in all cases must be direct if inter alia it refers to an opinion or to grounds on which that opinion is held. It must be the evidence of the persons who hold the opinion on those grounds.

A distinction must be drawn, however, between the cases where an opinion may be admissible u/s 6 to 11[3] as forming a link in the chain of relevant facts to be proved and between cases where opinions are admissible under sections 45-51.[4] The former evidence is given by the non-expert or the unskilled witness while the latter is given by the expert witness. Thus, in matters of calling for special knowledge or experience or skill, opinions of expert witnesses are relevant u/s 45-51.

Prerequisites of expert evidence:

For the sake of consideration of expert testimony, there are two important conditions that are necessary to be shown:

1. That the subject is such that expert testimony is essential.
2. That the witness in question is really an expert.[5]

It must be proved that the witness is competent enough to give the evidence and that the fact to be proved a point of science or art of which the witness is an expert in, before the opinion of a person can be admitted in evidence.[6]

If A witness is not proved to be an expert. His opinion will become irrelevant. It must be proved that the witness is an expert. He must be examined as a witness in the Court and be subject to cross-examination.[7]

Who is an expert?

Section 45 defines an expert as a person who is especially skilled in a given field. An expert is a person who has special knowledge and skill in a particular calling to which the inquiry relates. An expert witness is one who has devoted time and study to a special branch of learning; this is especially skilled on those points on which he is asked to state his opinion. His evidence on such points is admissible to enable the tribunal to come to a satisfactory conclusion.[8]

The section does not refer to any particular attainment, the standard of study or experience, which would qualify a person to give evidence as an expert. All persons who practice business or profession which requires them to possess certain knowledge of the matter in hand are experts, so far as expertness is needed. It is the duty of the judge to decide whether the skill of any person in the matter on which evidence of his opinion is offered is sufficient to entitle him to be an expert.

Opinion:
It is estimation, a belief or assessment, a view held as probable, what one thinks about a particular question or topic, an assessment short of grounds of proofs, a formal statement of reasons for the judgment, a formal statement of professional advice.

Competency And Credit of An Expert

Under Section 45 of the Indian Evidence Act, the evidence of an expert can be led on a question of foreign law, etc., to enable the tribunal to come to a satisfactory conclusion. It is for the Court to decide the competency or fitness of a witness.

The test is to see if the witness is sufficiently qualified by experience.[9] His credit can be challenged by cross-examination, or by the contrary evidence of another expert or by showing that he had expressed a different opinion on the same question previously or in any of the modes allowed u/s 146 to 153 and S. 155 to impeach the credit of a witness generally.

The Questions put to an expert are generally hypothetical as they assume something for the time being. An expert witness must himself come and give evidence in court. His certificate cannot go in automatically without proof unless permitted by statutory exceptions like. 509 (medical certificate), or section 510 or the CrPC (report of the chemical analyst).

When the expert evidence is presented by the prosecution particularly, the expert Must not assume the role of an advocate. The expert is not supposed to ask or to give his opinion regarding an issue in the case and he should not become a Part in the functioning of the Court.

Because even though the expert may state his opinion, the prosecution presents his opinion in relation to the guilt of the accused when the judge accepts it as it is and delivers the judgment accordingly such as judgment is not the result of interpretation of available Evidence, but it violates the mandate of S. 45 of Indian Evidence Act. An expert opinion according to S.45 is not conclusive proof of the guilt of the accused but merely a relevant fact for deciding the fact in issue.

The Courts have full powers to derive its own conclusion upon considering the opinion of the experts, which may be adduced by both sides, cautiously, and upon taking into consideration the authorities on the point on which he deposes. The opinion could be admitted or denied. Whether such evidence could be accepted or how much weight should be given thereto, lies within the domain and discretion of the Court. The evidence of an expert should, however, be interpreted as any other evidence.

Thus, it can be concluded that the expert opinion in numerous matters relating to identification of thumb impression, handwriting, footprints, fixing paternity, time of death, age of the parties, cause of death, possibility of the weapons used, disease, injury, sanity and insanity of the parties and other question of science or trade has become the need of hour and the person having required skill on that subject (called experts), are allowed to give their opinions in evidence as well as testify to facts/details leading to their opinion.

The opinion of an expert having a special skill in that particular field is relevant to the point of admissibility before the Court of law. There may be exceptions to this rule; in spite of it, when their direct evidence is lacking, then to corroborate the existing evidence, expert opinion is sought.

Evidentiary Value of Expert Opinion

The Opinion of an expert must be of corroborative nature to the facts and circumstances of the given case. If the opinion contradicts an unimpeachable eyewitness or documentary evidence, then it will not have the upper hand over direct evidence. The Section does not provide for any specific attainment of knowledge or study or experience for, being called an expert. Experts are admissible as a witness but, they are not to make a conclusion as it is a judicial function.[10]

In Forest Range officer v. P. Mohammad Ali[11], it was held that expert opinion is only the opinion evidence. It does not help the Court in interpretation. The mere opinion of an expert cannot override the positive evidence of the attesting witness.[12] Expert opinion is not necessarily binding on the Court.[13]

In Muralila v. State of Madhya Pradesh[14], it was held by the Supreme Court that there is no justification for condemning the opinion evidence of an expert to the same class of evidence as that of an accomplice and insist upon corroboration.

The court also stated that it would be a grave injustice to base a conviction solely on the opinion of handwriting expert or any other kind of expert, without substantial corroboration. An expert deposes and not decides. His duty is to furnish the judge with the necessary scientific criteria for testing the accuracy of his conclusion so as to enable the judge to form his own independent judgment by the application of these criteria to the facts proved in evidence.

Foreign law:

Law Which is not in force in India, is foreign law. In England, it can be proved by leading expert evidence. In India, it may be proved the same way under section 45 or by producing of official books and reports on foreign law u/s 38. Foreign law is, therefore, a question of fact.[15] Hindu law and Mohamedan law are laws of the land, and it is the duty of the court to interpret the law of the land, and hence, the opinions of experts, however, learned will be irrelevant.[16]

Science or Art:

The Expression Science or Art includes all subjects on which a course of special study or experience is necessary for the formation of an opinion. The words science and art are, therefore, to be broadly construed; the term ‘science’ not being limited to higher sciences and ‘art’ not being limited to fine arts.

To determine whether a particular matter is of a scientific nature or not, the test to be applied is whether the subject matter of inquiry is such that inexperienced persons are unlikely to prove capable of forming a correct judgment without the assistance of experts.

Medical Experts:

The The deposition of a medical officer in the court and the reports produced by him are considered as evidence. A mere post-mortem report, however, is no evidence since no facts could be taken from it.[17]

Value of Medical Evidence:

Expert Evidence should be approached with care and caution. An expert witness, however, impartial is naturally biased in favor of the party who calls him.[18] He is often called by one side simply and solely because it has been ascertained that he holds view favorable to his interest[19].

Medical evidence isn’t direct, and, therefore, the value of such evidence lies only on the extent to which it supports and lends weight to the direct evidence of eye-witnesses or contracts that evidence and removes the possibility that the the injury could take place in the manner alleged by those witnesses.[20] The opinion of a doctor is entitled to great weight but maybe discarded on good grounds.

The the opinion of Handwriting Expert:

U/s 45 of the Indian Evidence Act an expert can depose to the identity of handwriting between the questioned document and the document admitted or proved. Disputed handwriting may be proved either by calling an expert (S.45) or by examining a person acquainted with the handwriting of the person by whom the a questioned document is alleged to have been written (S.47) or a comparison of the two u/s 73.

However, the opinion of a handwriting expert is only made admissible; it is not the only Method of proving to handwrite [21].

In Fakhruddin v. State of M.P.,[22] the SC suggested three modes of proof of document: firstly, by Direct evidence, secondly by expert’s evidence and thirdly, by the court coming to a conclusion by comparison.

Finger-impression:

A The man’s signature is called an unforgettable signature. This head was added to Expert evidence’s scope in l899. The study of fingerprints are generally Admitted to constitute a science. Its two basic hypotheses are that:

1. Firstly, fingerprints of a person remain the same from birth to death;
2. Secondly, there has never yet been found any case where pattern made by one finger exactly resembled the pattern created by any other finger of the same or any other hand.

The the opinion of thumb impression expert is entitled to greater weight-age than that of a handwriting expert.

Firearms Experts:

Ballistic Expert Evidence: Ballistics is the science that deals with the motion, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and hurling projectiles so as to achieve the desired performance.[23] Where the opinion is given by the Expert of Ballistics who, after conducting all the tests, deposes in the Court of law, there is no reason to distrust his opinion. It can be accepted.[24]

That does not mean, in spite of having direct evidence, one should call for the opinion of the expert. In every case where a firearm is alleged to have been used by an accused person, in addition to the direct evidence, the prosecution must lead the evidence of a ballistic expert, however good the direct evidence may and though, on the record, and there may be no reason to doubt the said direct evidence.[25]

Where the ballistic expert has not seen the wound himself but has given his opinion based upon the recordings or photo produced by the doctor who saw or inspected the wound, and no reliance can be placed on such expert opinion.[26] Therefore, the firearms or ballistic expert must have concluded the opinion based on his own findings and personal observation.

Footprints:

Footprint Identification is reliable. Our bare feet contain friction ridge patterns that are unique to each individual. Hence, the fingerprints and footprints found at the scene of offense can be used to help identify the offender. They can be used for identifying the victim as well. The validity of the scientific method used for fingerprinting and the Courts accept footprinting. In Pritam Singh vs. State of Punjab[27], disputed footprints in blood near a dead body and going towards the bathroom were compared with those of the accused taken in printer’s ink.

The expert gave evidence giving points of nine similarities in respect of the right foot and ten in respect of the left foot: And three dissimilarities only in each case and explained the dissimilarities with reference to the different densities of blood and ink. It was held that the comparison stood the test well, and under the circumstances, these foot impressions in blood near the place of the incident were proved to be those of the accused.

Deoxyribonucleic Analysis (DNA):

Each A person's genetic makeup contains DNA. This differs from individual to individual. DNA can be obtained through blood, saliva, semen, or hair. This helps in identifying a person. If a drop of blood or a strand of hair is found at a crime scene, it can be compared to a person's known DNA to see if there is a match, thereby linking the person to the crime.

An expert witness can give an opinion about the likelihood that the blood that was found at the crime scene came from the individual whose sample was compared. The DNA analysis is also used to establish paternity. Experts believe that the ability to link the culprit to the crime scene through his DNA prints is unquestionable as unlike conventional fingerprints that can be surgically altered, DNA is found in every tissue, and no known chemical intervention can change it.[28]

Lie Detector:

Generally, Courts refuse to admit the results of a polygraph test as evidence. The polygraph measures a person's unconscious physiological responses, such as breathing, heart rate, and galvanic skin response while the person is being questioned.

The underlying theory is that stress occurs when a person lies and that this stress is measured by changes in the person's physiological responses. There is a concern that an individual can conceal stress when he or she is lying. Polygraph tests are also considered unreliable because it is not possible to tell whether the test itself or causes the stress that is measured during the test by a lie.

Various Rules For Expert Opinion

1. The first rule is of expert educational background. That means even the doctor is examined and is subjected to scrutiny and cross-examination. And if his opinion and observations contained in his statement are supported, then the report can be looked at otherwise not. So, even the examination of a doctor becomes essential.[29]
2. The second test is of the exhibits and the illustrations that the expert brings with him or makes. He should not base his opinion on the basis of memory and abbreviated notes. But he should have the opinion of such a level that even if there is expert evidence of the opposite party, then also, he is able to defend his stand.
3. The third test is of readiness to detail his techniques and procedures. An expert should not be of skillful nature to outlining the procedures that he has followed. And he should be so confident that no qualms can say that he has skipped procedures in reaching his own conclusions.[30]
4. And the conclusive test is that an Expert is conservative and is cautious.[31] It is a well-settled principle that the opinion of an Expert should be taken with great caution, and moreover, the decision should not be based simply on the basis of the opinion of an Expert, without a substantial corroboration, as it is unsafe otherwise. The opinion of an Expert by its very nature, weak, and infirm and in itself cannot of itself form the basis for a conviction and should be taken with great caution.[32]

It is their duty of court not to occupy the role of an expert by themselves and S.C. has always deprecated the courts to take the role of an expert. But before applying the opinion of an expert, the court has to see to apply it's own admitted or proved things and compare them with the disputed ones. And they have to verify the premises of the expert in one case and value the opinion in the other case.[33]

When the direct evidence is well corroborated by the circumstantial evidence and conforms to probabilities, and there is no reason why it should not be accepted. The mere fact that the expert has come to a different conclusion on a particular point would not render that part of his story open to doubt , especially when the data on which the expert has come to that conclusion is insufficient. The data on which the expert weighs must weigh with the Court, and the opinion of the expert must be judged in the light thereof.[34]

Conclusion
This provision is based on the principle that as judges are not properly equipped to to draw proper inferences from the facts stated by witnesses, and it is Appropriate that the opinion of an expert must be taken into consideration. But the expert’s opinion is a weak form of evidence, especially in the cases where the sufficiency of knowledge is doubtful.

An Opinion or belief may be of an expert or a non-expert. A witness, in order to give an opinion, must be competent, and the subject matter must be one in respect of which an opinion is allowed. The subject matters of an opinion involve skill in a particular trade or profession or special knowledge of a particular science or art. However, in matters of age, identity, or the condition of a person or thing, the belief of the witness is sometimes accepted when it is based on facts within his own knowledge. A jury, however, is entitled to accept or reject the belief or opinion of any witness.

As a general rule, the opinion of a judge, only plays a part and is thus relevant in the decision of a case, and therefore, the opinion of any person other than the judge about any issue or relevant fact is irrelevant in deciding the case. The reason behind such a rule is that if such opinion is made relevant, then that person would be invested with the character of a judge. Thus, Section 45 Is, therefore, an exception to this general rule, as it permits the experts' Opinion to be relevant in deciding the case.

The reason behind this is that the Judge cannot be expected to be an expert in all the fields-especially where the subject matters involve technical knowledge as he is not capable of drawing an inference from the facts which are highly technical. In these circumstances, he needs the help of an expert- who is supposed to have superior knowledge or experience in relation to the subject matter.

End-Notes
[1] Hodge M Malek and Sidney Lovell Phipson, Phipson on Evidence (1979).
[2] Areti Krishna Kumari, 'Evidentiary Value Of Expert Opinion Under Indian Evidence Act', SSRN Electronic Journal (2007).
[3] Indian Evidence Act, l872, § 6 – 11.
[4] Indian Evidence Act, l872, § 45 – 51.
[5] Parat v. Bissessar, ILR 39 Cal 245.
[6] Raj Kishore v. State, AIR l969 Cal 321.
[7] Balkrishna Das Agarwal v. Radha Devi, AIR l989 All 133.
[8] R. N. Choudhary, Expert Evidence (2nd ed., Oriental Publishing Company, 2004).
[9] Gopeswar v. Biseswar, l6 CWN 265 (285).
[10] Charles Dickenson Field, C.D. Field's Commentary on Law of Evidence Act (Delhi Law House, 12th ed. 20ll).
[11] Forest Range Officer v. P. Mohammad Ali, AIR l994 SC l20.
[12] U.Jhansi Lakshmi Bai v. P.Mohammad Ali, AIR l994 SC l20.
[13] Las Society of India v. Fertilizers and Chemicals Travancore Ltd., AIR l994 Ler. 308.
[14] Murali Lal v. State of Madhya Pradesh, l980 SCR (2) 249.
[15] Khoday Gangadhara v. Swaminath Mudali, 1926 Mad 218.
[16] Aziz Bano v. Mohd. Hussain 47 All 823.
[17] Ramswaroop Masawan vs Municipal Council and Anr., AIR l999 SC 705.
[18] Y. H Rao and Y. R Rao, Expert Evidence, Medical & Non-Medical (LexisNexis Butterworths Wadhwa Nagpur 2011).
[19] Divan Singh v. Emperor, 43 Cr. LJ 565.
[20] Nagindra Bala v. Sunil, l960 AIR 706.
[21] State v. Tribikram, (1971) 37 Cut LT 714.
[22] Fakhruddin v. State of M.P., AIR l967 SC 1326.
[23] 'Ballistics' (En.wikipedia.org) accessed 15 Sept. 2019.
[24] Surat Singh vs. State, 1995 Cr.L.J. 3189.
[25] Kartik Harijan Vs. State of Orissa, l995 CrL.J. 2019.
[26] Mohan Singh v. State of Punjab, AIR l975 SC 2161.
[27] Pritam Singh And Anr. vs The State of Punjab, AIR 1956 SC 415.
[28] 'Offenders Beware: DNA May Be Evidence Soon' (Rediff.com, 2oo6) accessed 15 Sept. 2019.
[29] Dhobi Yadav v. State of Bihar, AIR l989 (2), Cr. L.C., 629 at p 641.
[30] C. K. Johari, IDENTIFICATION OF FINGERPRINTS & LAW, 2 J.T.R.I. JOURNAL, 1-5 (1995).
[31] Id. at 12.
[32] Magan Bihari Lal v. State of Punjab, AIR 1977 SC 1091.
[33] Joginder Prasad v. Joy kanta Roy, AIR 1971 Assam 168.
[34] Brij Basi v. Moti Ram, AIR 1982 All 323 at p 321.