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The Expert and The Lawcourt
by K. Kumar *

Cite as : (1987) 4 SCC (Jour) 7


It is the fundamental principle of law of evidence that witnesses should State facts which are within their knowledge and forming of an opinion on any matter under enquiry is within the domain of the court. However, there are situations when the Court is not in a position to form its judgment on certain issues without the aid of persons who have acquired special skill or experience or knowledge in certain areas that are beyond the common experiences of men. When a situation like this arises, the rule is relaxed and conclusions drawn from a set of facts by specially skilled persons are admitted in evidence under the provisions of Section 45 of the Evidence Act (1872):

"When the court has to form an opinion upon a point of foreign law, or of science, or art, or as to identity of handwriting or finger impressions, the opinions upon that point of persons specially skilled in such foreign law, science or art, or in questions as to identity of handwriting or finger impressions are relevant facts.

Such persons are called experts."

From the moment an expert witness is introduced in the court as a witness, he becomes an object of intense interest and according to Lord Russell1, the following questions should invade the mind of the Judge:

(a) Is he peritus?

(b) Is he skilled?

(c) Has he adequate knowledge?

Leonard Caplain2, has outlined four qualities of an expert witness described below:

1. Expertise.—It may appear to be absurd to say that an expert witness lacks expertise but it is not so. A medical expert witness holding a recognised medical degree may technically be a qualified expert witness but he may lack expertise in the absence of a thorough grounding in post-mortem work. The question of expertise may be decided on the basis of an enquiry into the academic qualifications, professional training, experience of work in the relevant branch of the subject, facilities at the command of the expert to do the work and application of those means in the work.

2. Clarity.—This is something which the expert witness must express through the medium of simple language avoiding jargon. A man of true science having a clear understanding of the subject used, but a few hard words whereas the less knowledgeable persons try to impress through the medium of harsh words. The expert witness should be able to express himself through simple language which could be followed even by a layman. In order to make things simpler, he should be able to explain through charts, photographs and sketches and make his evidence demonstrative.

3. Relevancy.—There should be relevancy in the conclusion of the expert's report and the findings should not be based on mere assumption or premise but on relevant data. The data could be his own or from the published work of accredited authors. He should be cautious and conservative and should know where not to commit.

4. Reliability.—The expert should not only be reliable but appear to be so and that he should satisfy himself against any bias.

(i) System of Cross examination.—An attorney is supposed to know less than the witness but in Court room environment he is in a position to put up an air of superior knowledge. At times, the witness loses his balance of mind and gets trapped in the net spread for him.

(ii) Expert being presented by parties.—Many a time, an expert is introduced in the Court by the party who pays for it. This results in an unconscious bias that the expert witnesses have the tendency to side with the party hiring him. Lord Jessel3, the Master of Rolls, expressed the following in this context in rather unduly harsh words:

"In matters of opinion, I very much distrust expert evidence. Although the evidence is given on oath, the person knows that he cannot be indicted for perjury. But this is not all. Expert evidence of this type is the evidence of persons who sometimes live by their business but in all cases are remunerated for their evidence. It is but natural that his mind should be biased in favour of the person employing him and accordingly we find such bias."

(iii) Text of the report.—The report or the opinion is yet the third source of bias. This is precisely the view expressed by the Supreme Court of India4 in a case where the medical officer had conducted the post-mortem examination. The case was of a death under suspicious circumstances where he reserved his opinion about the cause of death and had then noted in his report that "the tongue was inside the mouth" but had interpolated with words "mouth is closed with tip (something scored out) seen caught between the teeth" and "caught between the teeth" only after the receipt of the Chemical Examiner's report to support the view that it was a case of mechanical suffocation, was held not a mitigating circumstance in favour of PW (33), the Medical Officer. The doctor had tampered with the evidence in the case of alleged murder, may be at the instance of somebody else, ignoring the probable consequences of his act.

Reasonable doubt

An important philosophy of Criminal Jurisprudence is that a case should be proved beyond reasonable doubt. What amounts to a reasonable doubt has been expressed by the Privy Council in Water v. Rex5 in the following words:

"A reasonable doubt is that quality and kind of doubt which when you are dealing with matters of importance in your own affairs you allow to influence you one way or the other."

The views expressed by the Supreme Court of India6-7 on proof beyond reasonable doubt is as follows:

"The cherished principles or golden thread of proof beyond reasonable doubt which runs thro' the web of our law should not be stretched morbidly to embrace every hunch, hesitancy and degree of doubt. The excessive solicitude reflected in the attitude that a thousand guilty men may go but one innocent martyr should not suffer is a false dilemma. Only reasonable doubts belong to the accused. Otherwise any practical system of justice will then break down and lose credibility with the community. The evil of acquitting a guilty person light-heartedly as the learned author Glanville Williams in 'Proof of Guilt' has sapiently observed, goes much beyond the simple fact that just one guilty person has gone unpunished. If unmerited acquittals become general, they tend to lead to a cynical disregard of the law, and this in turn leads to a public demand for harsher legal presumptions against indicted 'person' and more severe punishment of those who are found guilty. Thus, too frequent acquittals of the guilty may lead to a ferocious penal law, eventually eroding the judicial protection of the guiltless. It is true to say, with Viscount Simon, that 'a miscarriage of justice may arise from the acquittal of the guilty no less than from the conviction of the innocent...'. In short, our jurisprudential enthusiasm from presumed innocence must be moderated by the pragmatic need to make criminal justice potent and realistic."

Reasonable doubt in science8 facilitates the exchange of ideas and the testing of hypothesis and theories.

In science there is no positive or absolute certainty and the scientist has doubts about everything. When the question of identity is involved there can only be a high degree of probability of things having a common origin on the basis of a large number of similarities but there cannot be an absolute identity. But when two things are demonstratively different there is no doubt that they are different. Thus a scientist can be positive about his negative finding but cannot be 100% positive about his positive finding.

The word IDENTITY in science means two objects are same in all respects and are indistinguishable by all the tests. Nothing except the fundamental physics particles or the atoms of the same isotope of an element can have complete identity. Even the smallest amount of material when seen under a powerful microscope will reveal the presence of several million atoms. A slight contamination will introduce a great change in the composition. If the standard of proof on the question of source correspondence be insisted upon a conclusion from identity instead of a high degree of similarity, then opinion on the origin of two articles from the same source cannot be formed.

In State of Gujarat v. Adam Fateh Mohmed Umatiya9 the Ballistics Expert failed to make himself intelligible to the Court. His opinion was discussed thus:

"The expert gave the opinion that the empty cartridges were fired from the rifle because of arch-like projection on the base of the cartridges produced by the defect in the rifle. The expert took photographs of two out of the four empty cartridges. He also took photographs of the test cartridges. He compared the photographs of the empty and the test cartridges and came to the conclusion that marks on the photographs were similar. He, however, did not take photographs of the misfired cartridge. It was also his evidence that the marks on the test bullet were indistinct and therefore it was not possible to compare satisfactorily the marks on the bullets which had been sent by the police to him. He could not say that the jacket cap of the bullet sent by the police was a bullet which had been fired from the rifle.

The witness further said that he did not compare the marks of misfired cartridges with those of empty cartridges. The witness said that the striker scrapes on the test cartridges and on the empty cartridges were not indentical but similar. The witness also said that when a striker strikes the cap normally the mark would be circular. In the empty cartridges the mark was of an eye-like shape and the witness said that it was because of a defect in the gun. In the photographs of the empty cartridges there was on the cap a mark which was roughly roundish. The witness said that the entire bulge was called the scrape. The differences between the test cartridges and empty cartridges were vital and varied. The photographs of the test cartridges and of the empty cartridges revealed that there were black spots on the test cartridges which did not tally with the black spots on the empty cartridges. The witness admitted that photographs were necessary for comparison. He took no photograph of the misfired cartridge."

In the circumstances the Court held that —

"The second reason given by the expert witness that bulge marks on the test cartridges and bulge marks on the empty cartridges were similar but not the same cannot establish that the empty cartridges were fired from the same rifle."

Commenting on the evidence the Court said,

"The bulge marks on the empty cartridges were of the shape of an eye. The expert witness did not take composite photographs of the empty cartridges superimposed by the test cartridges. The photographs which were taken were not taken in the same condition of light.

.... The expert did not find any dents on the two empty cartridges. His evidence was that the indentation mark was the peculiarity of the rifle. The expert could not give any reason for the presence of dents on the test cartridges and the absence of dents on the empty cartridges. If indentation marks were different at the base of the cartridges that would show that they were not fired from the same weapon. The evidence of the expert cannot, therefore, be relied upon to hold that the empty cartridges were fired from the rifle in question. It is true that Accused 1 made a statement resulting to the discovery of the rifle but that would not be sufficient to connect Accused 1 to the crime."

In this case, the expert must blame himself for rejection of his testimony. The salient features of the report are as follows:

(1) Only arch-like projection over the back of the cartridge, produced by the defect of the rifle cannot be a ground for holding that all such cartridges having arch-like projections were fired by the same rifle unless the arch-like projections were similar in nature.

(2) The expert failed to explain before the court that there cannot be absolute identity between two objects and they can never be the same. Very close similarity between the marks could indicate a high degree of probability consistent with the conclusion of the marks being caused by the same source.

(3) Under the Comparison microscope, the cartridge shells or the bullets are compared and the enlarged view of the marks on the test and the crime cartridges/bullets are seen side by side and compared. In this case comparison is done through photographs. The Supreme Court in an elaborate judgment in Ramanathan v. State of Tamil Nadu10 has held:

"A comparison microscope consists essentially of two compound microscopes, having identical optical systems, so that they give the same magnification, connected by an optical 'bridge' containing a combination of prisms such that by viewing two separate objects (one under each microscope) through a single eye-piece the two objects may be compared by bringing the images of parts of each into juxtaposition."

(4) If the marks on the test bullets are distinct, that is no ground for holding that it was not possible to compare satisfactorily the marks on the bullets that had been sent by the police to him. Perhaps the mark on the crime bullet was indistinct and uncomparable.

(5) It is not correct to say that when a striker strikes the cap normally the mark would be circular and since the mark was of oval shape like an eye, it was due to defect in the weapon.

(6) The black spots on the test cartridge cannot be due to any difference of the striker mark. Rather it could be due to something else, such as some dust or dirt adhering to the tip of the firing-pin or over the percussion cap.

(7) Bulges and scrapes are two different phenomena although both may coexist.

Disputed paternity cases

Disputed paternity cases can be decided conclusively by serological tests although, at times, the serological tests may be in conflict with presumption in law. Law presumes that the husband of the woman, who bears the child is the father. Some Courts have held the presumption to be almost rebut table.11 There are four groups in the ABO system and heredity of the child depends upon the parental combination as per the Bernstein theory.12

Parents Children Offspring

Phenotypes Genotypes Genotypes Phenotypes Offspring

O & O OO & OO O O A, B, AB
O & A OO & AO
A & O AB & B
O & B OO & BB
B & O AB & A
A & A AA & AA
A & O B & AB
A & B AA & BB
AO & BO    
O, A, B, AB None
B & B BB & BB
B & O A, AB
O & AB OO, AB AO & BO A & B O, AB
A & AB AA & AB
A, B, AB
A & B
B & AB BB & AB
A, B & AB
A, B, AB

In the case of Hargovind Soni v. Ramdulari13 the husband claimed divorce from his wife on the ground of adultery on the basis of presumptive proof upon certain circumstantial evidence, such as non-access of wife before the husband, birth of children during the period of separation and contacting venereal diseases. The wife had left the house of husband consequent on husband having contracted second marriage as the wife was reported to be barren. After a couple of years of abandonment, the wife delivered a male child on 12-3-1969, a girl on 27-5-1975 and another female child on 1-5-1979. The husband denied any access to the wife and the wife's claim was that the children were born out of her connection with the husband which had continued thereafter. The Gwalior Bench of M.P. High Court decided the issue by subjecting all of them to serological tests performed by Dr Sarla Monga. The result of the tests were as under.

Sr. No. Name Group

1. Father (Hargovind Soni) B
2. Mother (Ramdulari) O+ve
3. Son (15 yrs) Rajkumar O+ve
4. Daughter (10 yrs) Seema O+ve
5. Daughter (5 yrs) Rajni A+ve

There was, thus no possibility of Rajni, being the offspring of the petitioner, because when the parents belonged to group B and O, offsprings of the groups A and AB are excluded. The other two children had inherited the blood group of the mother and could or could not be the offspring of Hargovind Soni. The Court thus allowed the divorce suit with cost of maintenance to the wife and the first two children.

In another case reported from M.P., Gulabi Bai was claimed by two sets of parents (1) Girwar and Shetan Bai and (2) Kaluram and Roshan Bai. The usual ABO group test could reveal that she could be the offspring of any one of the two. Further analysis by immunological test excluded one set of parents. Working on more number of parameters give positive and conclusive results.

Importance of increasing the number of parameters — The distribution of various groups in the population is as follows14:

43% 42% 12% 3%
90% of the population is Rh+ve and only 10% is Rh negative.

If, therefore, a person is AB — ve, the frequency of the distribution in the population of a person of this group is

3   10   3    
x x = i.e.; one person in 333 persons.
100   100   1000    

The London Metropolitan Police Laboratory in London is getting analysis of blood done on 14 parameters, i.e. (i) ABO, (ii) Rh., (iii) MN, (iv) Kell, (v) Dalty, (vi) Kidd, (vii) GM, (viii) Ge, (ix) Heptaglobin, (x) Phosphoglucomutase (PGM), (xi) Adena Oino Deaminase (ADA), (xii) Erythrocite Acid Phosphatase, (xiii) Glutamala Pyriate (GDI), (xiv) Eastrase-D (ESD). This gives an assurance of presence of one in a population of 1/4 X 10-10. A person can, therefore, be individualised from his blood analysis. This is analogous to individualisation of persons by fingerprint and is conclusive.

Corpus delicti

Corpus delicti is the body of evidence and includes the dead body of the victim apart from other evidences such as recovery of a bullet from the dead body in case of death by gunshot injuries or clothing bearing marks of injuries or photographs showing injuries on various parts of the body. The corpus delicti can be proved if the medical examiner or the witnesses establish the fact that the individual was dead. It is not impossible to present unclaimed decomposed dead bodies or fragmentary human remains to support false charge of murder against adversary.

Lyon reports a case where one Ibrahim Beg, a wealthy mahajan. was convicted for the alleged murder of his wife, Chumbelee. On the day prior to the date of execution of the convict, an individual informed an English civilian that Chumbelee was alive and was kept in hiding by a gang of fakirs. Subsequently it was revealed that the whole affair was a conspiracy hatched by a man known as Khan Beg. He, with the assistance of a servant, Mohammed Jan, excited the jealousy of the husband who beat his wife. Her loud screams were heard by neighbours. After this, she was abducted and made over to the fakirs. The conspirators got hold of a female dead body, cut off her head, put on in the arms of the corpse, Chumbelee's bangles and buried it in the courtyard of Ibrahim Beg's house. The man who informed that Chumbelee was still alive, was a subordinate in the whole affair and disclosed the conspiracy as he was not paid the expected remuneration.

Darshan Singh and two others were convicted to a sentence of life imprisonment by the Court of Session, Faridkot (Punjab) for the alleged murder of a boy, Sajjan Singh (15 years). While the case in appeal was being heard by a Division Bench of the Punjab and Haryana High Court at Chandigarh, the murdered boy walked into the Court-room along-with his father and startled everybody. This happens when corpus delicti is not proved properly.

Admissibility of a novel technique in evidence

Courts of Law are traditionally conservative in nature and change their views with extreme caution. In addition, the previous judgment by a superior court becomes binding on a trial court, of the rulings of Supreme the Court on a High Court and all other Courts under Article 141 of the Constitution.

The Courts in the U.S. have viewed the problem of relevancy as the basic issue concerning the admissibility of scientific and technological evidence. Frye v.U.S., decided in the year 1923, established the standard concerning the admissibility and relevancy of technological evidence. The Court in this case enunciated the test of general acceptance in the admissibility of Polygraph evidence:

"Just when a scientific principle of discovery crosses the line between the experimental and demonstratable stage, is difficult to define. Somewhere in this twilight zone, the evidential force of the principle must be recognised and when Courts will go a long way in admitting expert's testimony based on well-recognised principles of science, these techniques must be sufficiently established to have gained general acceptance in the particular field in which it belongs."

One problem which exists with the standardisation of method consists in the fact that scientists consider it as an infringement on their ability to develop or choose their own methods for analytical work. The Courts also are aware of the fact that science is progressing by leaps and bounds and in India, the Courts accept the superiority of novel techniques.

In Goverdhanlal v. Commissioner of Police15 the report of the Public Analyst was attacked and its reliability challenged because the Public Analyst had used TLC method instead of the usual HC1 method to find whether the groundnut oil was adulterated with agromine oil. The State Counsel presented the Public Analyst before the Court who could prove through literature, etc. that TLC method was sophisticated and more sensitive. The High Court in that case ruled as follows:

(i) The Public Analyst produced register showing that the TLC method was used in all such analysis.

(ii) Another sample when subjected to TLC test showed negative result for the presence of agromine oil. This proved that TLC test is devoid of biased results.

(iii) Analysis by TLC is sophisticated and more sensitive. The sensitivity of HC1 method of analysis is 0.1 % whereas that of TLC is 0.005 %. This has been proved through filing of scientific papers.


It is not only the scientist who can play a role in bringing about an improvement in scientific methods and techniques but the Lawcourts can play a major role in it by (1) demanding better scientific evidence on improved and sensitive methods of instrumental analysis and proper interpretation of results. (2) by meticulously examining the contents of a report and asking searching questions from the experts who present the evidence. (3) where convinced, the Courts may encourage the scientist and recognise the particular method through their judgments.

Improved techniques can render very useful service to the administration of criminal justice.

* Advocate Supreme Court of India. (Formerly State Examiner of Questioned Documents, Ballistics Expert and Asst. Chemical Examiner to the Government of Bihar and Asst. Director (Ballistics), I.C.F.S. (MHA), Government of India. Return to Text

  1. Rex v. Silverlock (1894) 2 QB 766 Return to Text
  2. Caplain, L, (1979), The Medicolegal Journal, Vol. 47, Part 4, p. 124-137 Return to Text
  3. Abinger v. Asthoa, L.R., 17 Equity Return to Text
  4. Sharad Birdhichand Sarda v. State of Maharashtra, (1984) 4 SCC 116 (211) Return to Text
  5. (1969) 2 AC 26 PC Return to Text
  6. Shivaji Sahabrao Bobade v. State of Maharashtra, (1973) 2 SCC 793 : 1973 SCC (Cri) 1033 Return to Text
  7. State of U.P. v. Pussu, (1983) 3 SCC 502 : 1983 SCC (Cri) 713 Return to Text
  8. Ian Holden, PhD, FRIC, "What amounts to a reasonable doubt?" Medicolegal Journal, Part 2, 1973, p. 63 Return to Text
  9. (1971) 3 SCC 208 : 1971 SCC (Cri) 381 Return to Text
  10. (1978) 3 SCC 86 : 1978 SCC (Cri) 341 Return to Text
  11. Demanding Scientific Evidence, Journal of Forensic Sc. Society, Vol. 7, No. 4, Oct. 1967. Return to Text
  12. Gonzales et. al (1954), Lega; Medicine, Pathology and Toxicology, 2nd Edn., Appleton and Century, N.Y., U.S.A., p. 642 Return to Text
  13. AIR 1986 MP 57 (Gwalior Bench) Return to Text
  14. Shefferstein, R., Criminalistics-An introduction to Forensic Science, Prentice Hall, Inc., England, Cliff, N. J., U.S.A. Return to Text
  15. 1975 FAJ 363 (AP) Return to Text
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