Witness in forensic science

All persons are competent to testify unless they are prevented from understanding the questions put to them, or from giving rational answers to those questions, due to tender years or extreme old age or disease.

Types: Witnesses are of two types:

(1) Common, and

(2) Expert.

Common witness (witness of fact or occurrence witness) is a person who gives evidence about the facts observed or perceived by him. He must show that he was capable of perceiving the fact by one of his own senses, and that he actually observed this fact.

This principle is commonly known as the “first-hand knowledge rule”, which may be used to establish the exact circumstances of the case for the Court, e.g., A has seen B and C, fighting with sticks on a certain road on particular day and time. In a case of traffic accident the person who witnessed the accident becomes a common witness.

Witness in forensic science

Expert witness is a person who has been trained or is skilled or has knowledge, experience or education in technical or scientific subject, and capable of drawing opinions and conclusions from the facts observed by himself, or noticed by others, e.g., doctor, firearms expert, fingerprints expert, handwriting expert, etc.

An expert witness may give his opinion:

(1) upon facts which are either admitted, or proved by him or other witnesses at the trial,

(2) on matters of common knowledge, and

(3) on hypothetical questions (questions based on stated assumptions) based there on.

Hypothetical questions may be asked to extract an opinion from the expert, after he assumes certain facts to be true, describing a specific situation, even though he may not have first-hand knowledge of the actual case. The expert should hesitate for a moment, so as to give the opposing lawyer an opportunity to object to the question.

The answer should be given only after completely understanding the question. The main obligation of an expert is to point out professional facts. But, he may be asked to give professional estimate which his observations seem to justify, e.g., whether or not an injury is caused in the manner alleged or from the causes assumed; the possible consequences; the reasonable estimate of damages, etc.

A doctor’s testimony that a certain thing is possible is no evidence at all. A doctor’s testimony can only be considered evidence when he states that the conclusion he gives is based on “reasonable medical certainty” (more probable than not in a medical sense) that a fact is true or untrue.

In other words, if the likelihood of an event is more probable than not given the facts, the physician can testify with a reasonable medical certainty. The opinion on a key question must be given in a more guarded manner using terms, such as that the findings are “consistent with” an alleged form of trauma, such as a fall against a hard object or with the striking of the head with a blunt instrument of a particular type or a blow from a fist.

It does not exclude other mechanisms which could reasonably or possibly have caused the same findings. If he is so excessively cautious as to confuse possibilities, probabilities and certainties, his testimony will become ineffective. Conclusions must be based on facts. Conclusions are much more important than opinions.

The expert who inspite of provocation, answers questions with goodwill and accuracy, and who does not make statements that he cannot defend, will be successful under such attack. Clear presentation and ability in expressing a relatively firm opinion are helpful for success of the expert.

The medical evidence does not itself establish the guilt or innocence of the accused. In the majority of cases, it provides expert opinions based upon objective, indisputable facts, which help to evaluate the reliability and credibility of other witnesses. The doctor is not a witness of truth. The expert evidence is of little value, when there is a conflict of opinion between experts. In such cases, the Courts usually accept that opinion which is not in conflict with direct opinion.

If there is difference between medical evidence of two doctors, one of whom examined the injured person and the other conducted the autopsy on the injured person after his death, as to the injuries, or the weapon used, or the time of infliction of injuries, etc., the accused gets the benefit of doubt.

Where the direct evidence is not trustworthy, conviction may result on medical evidence, if that is trustworthy. An expert witness may refer to books to refresh his memory, or to correct or confirm his opinion. Books as such are not evidence, but if an expert refers to specific passages as representing his views, they may be taken down as his own evidence.

A witness may adopt the views of any authority as his own, provided he has an honest belief in them. The opinion of an expert can be proved false by standard books on the subject.

A doctor can be both a common and expert witness. When he describes the wounds on the body, he acts as a common witness. But when he says that the wounds were antemortem or postmortem, or they were suicidal, homicidal, or accidental, or gives opinion regarding the cause of death, he acts as an expert witness.

Hostile witness is one who is supposed to have some interest or motive for concealing part of the truth, or for giving completely false evidence. The Court will declare a witness as hostile on the suggestion of the lawyer of the party who has summoned the witness or prosecution lawyer. On declaration of a witness as hostile, he can be cross-examined by the same side lawyer. Any of the above two types of witness can be hostile.


Perjury means giving willful false evidence. Whoever, being legally bound by an oath, or by an express provision of law to state the truth, or being bound by law to make a declaration upon any subject, makes any statement which is false, and which he either knows or believes to be false or does not believe to be true, is said to give false evidence. The witness is liable to be prosecuted for perjury, and the imprisonment may extend to seven years.

How is witness examined in forensic science?

The medical witness is allowed to sit in the Court if the lawyers of the accused do not object.


The evidence of the witness is recorded as follows:

Oath: The witness has to take an oath in the witness box before he gives his evidence. He should take the oath as follow : “I do swear in the name of God, that what I shall state shall be the truth, the whole truth, and nothing but the truth’. If the witness is an atheist, he has to “solemnly affirm” instead of “swearing in the name of God.”

Oath is a declaration required by the law, which is compulsory and holds the witness responsible for consequences of his evidence. A child below 12 years is not required to take an oath.

(1) Examination-in-chief (direct examination)

This is the first examination of a witness. It consists of questions put to him by the lawyer (counsel or advocate) for the side which has summoned him. In criminal acts committed by an individual or group, the State becomes a party instead of the aggrieved person, and starts criminal prosecution, which is titled as “State versus A”.

In a criminal trial, the burden to prove is always on the prosecution (adversarial system of trial), and the accused is presumed to be innocent till the contrary is proved against him. In Government prosecution cases, the public prosecutor, first examines the witness. If witness is called by private party, he is first examined by the lawyer of that party.

The object is to elicit all relevant, convincing medical facts, and the conclusions which the doctor has drawn from the facts. The doctor may have to interpret the findings of non- medical ancillary investigations provided by scientific laboratories, analysts and serologists, in all cases where the medical aspects are at issue.

Before giving evidence, it is advisable that the doctor meets the public prosecutor, and discuss the previously prepared report, the certificate of death, photographs, etc., that the witness intends to show in the Court, and an outline or pattern should be worked out for the best way to elicit his testimony.

If the witness intends to modify any of his findings or conclusions, these should be pointed out to the lawyer. The doctor should help the prosecutor in framing proper questions in proper sequence, so that all essential facts are elicited. The lawyer will be able to advice the doctor, about the anticipated content of cross-examination. In this leading questions are not allowed, except in those cases, where the Judge is satisfied that a witness is hostile.

A leading question is one which suggests to the witness the answer desired, or which includes a material fact, and admits of a conclusive answer by a simple “Yes” or “No”. “Was this injury caused by a sharp weapon?” Was the length of cut 3 cm?”. “Was it on the front of the abdomen?”. They are all leading questions, as they suggest the answer “Yes” or “No”.

The proper questions should be: “What type of weapon would cause this injury?” What was the length of the cut? Where was it seen”? The method of examination is by question and answer. The questions are usually short and demand some specific fact and short answer. But the answer can be given in narrative form, if it would be more informative and convincing. The effect of the questions and answers is recorded indirectly and not in the form of the question and answer.

(2) Cross-examination

In this, the witness is questioned by the lawyer for the opposite party, i.e., lawyer for the accused (defense lawyer), In a murder trial, the defense witness is cross- examined by public prosecutor.

The main objects are

(1) to elicit facts favorable to his case,

(2) to test the accuracy of the statements made by the witness,

(3) to modify, or explain what has been said,

(4) to develop new or old facts,

(5) to discredit the witness, and

(6) to remove any undue or excessive emphasis which may have been given to any of them.

In doing this, the lawyer may try to weaken the evidence by showing that the evidence given is inconsistent, inaccurate, ill- founded, contradictory, and untrustworthy. The cross-examination need not be confined to the facts to which the witness testified in his examination in-chief.

The competence and credibility of the witness is tested by questioning his qualifications, experience and the number of cases of the kind under consideration he has personally observed, and by testing his memory or powers of observation. When material is available, the lawyer may attack the character of the witness.

The witness may be asked questions on his bias or impartiality, his previous conviction, his reputation for untruthfulness and on any handicap he may have which would affect the reliability of his evidence. The Court will decide whether the witness should answer any particular question, when asked for a ruling.

The Court may forbid any questions which it regards as indecent or scandalous, unless they relate to facts in issue. The Court also has the power to disallow questions which are intended to insult or harass or offensive in form, but if they are relevant to the facts in issue, the Court cannot disallow them.

The witness has to answer any question relevant to the matter in issue, even though the answer will expose or prove his guilt directly or indirectly, e.g., which would reveal that he has committed an illegal operation. If a witness is forced to give an answer admitting his guilt, he cannot be arrested or prosecuted for it, and also it is not taken as proof against him in any criminal proceeding. A witness is completely immune from actions for defamation (libel or slander), for anything he says in the witness box.

Answers favorable to the defense side should be given as promptly as those given on examination- in-chief. There are few observations in medicine which are capable of only one explanation. If the defense puts points to the doctor which must be conceded, the doctor should reply that alternative explanations were considered, and on balance he prefers the conclusions already expressed.

Admit omissions, e.g. an examination of a drunken person may not require the use of all tests described in a treatise. This can be explained to the Court. Objectivity and impartiality are important against destructive cross-examination.

If a question is not audible, the witness should ask the lawyer to repeat the question. If the question is not understood, the witness should ask the lawyer to explain it better. If a question contains several different questions, each requiring a separate answer, the medical witness should ask the lawyer to break the question into individual components. The medical practitioner should not be dogmatic about his opinion and the lawyer should not expect him to be so. The witness should be clear, direct and precise in his answer, as far as possible.

He should not volunteer unrelated information. The defense lawyer may ask the witness, whether he talked about this case with anyone. The answer should be “Yes’. If asked with whom he talked, he should give the name of the lawyer by whom he was called to give evidence. If a further question is put, “What did you talk about?”, the most effective answer would be: “He told me to tell the truth”.

Sometimes, a previously published statement of his own, which may be in disagreement with what he is now stating is quoted against him. The effective answer should be, “medicine advances with the times, and I try to advance with its progress”.

If the defense succeeds in embarrassing or humiliating the witness, he may become tense, frightened, angry, hostile or aggressive, due to which his intellectual faculties suffer, and he will not be able to think clearly and effectively. When the reply to a question appears to damage the defense case, the lawyer may attempt to interrupt doctor’s answer by asking a new question.

The witness should say that he has not yet completed his answer to the preceding question. If the Judge rules in favor of the new question, the lawyer for the prosecution side will usually make a note of the question and its answer and will give the doctor an opportunity to complete his reply in re-examination.

The witness must answer a hypothetical question, but he cannot be compelled to answer a question that is based wholly or in part upon a subject, regarding which he cannot conscientiously reply. Leading questions are permissible during cross- examination. Cross-examination has no time limit, and may last for hours or even days. The Judge can always disallow irrelevant questions.

Objection to Testimony

When a question is asked of a witness, the opposing lawyer may say, “I object”, and give his reasons for the same. The witness should not answer the question until the Court gives a ruling on the objection. If the Judge says, ‘Objection overruled”, the answer has to be given.

The defense lawyer should not ask a question to which he does not know the answer, for the reply may strengthen the case of the opposite side and seriously hurt his own. Sometimes, cross-examination may act as a double-edged sword, i.e., it may damage the defense as much as the prosecution, especially if lawyer is not familiar with the subject and the witness is efficient and honest.

(3) Re-examination (Re-direct examination)

This is conducted by the lawyer for the side which has called the witness. The object is to correct any mistake or to clarify or add details to the statements the witness has made in cross-examination. It is an opportunity for the witness to explain more fully some answer which might appear damaging to his direct evidence, because of skilful questioning or tactics by the cross-examiner. The witness should not bring in any new matter at this stage. The opposing lawyer has right of re-cross-examination on the new point raised. Leading questions are not allowed.

(4) Questions by Judge

The Judge may ask any question, in any form, about any fact, relevant or irrelevant, at any stage of the examination to clear up doubts. The Court is also empowered to recall and re-examine any witness already examined, if his evidence appears to the Court to be essential to the just decision of the Court.

The deposition of the witness is handed over to him. The witness after carefully going through it, is required to sign at the bottom of each page, and on the last page immediately below the last paragraph, and to initial any corrections. The witness should not leave the Court without taking permission of the Judge.

Doctor as a Witness in Forensic science

The following rules help a doctor in the witness box:

(1) Be well prepared with the details of your evidence before entering the box; anticipate certain likely questions on it and be prepared to answer these in advance. It may be necessary to study the literature on the subject about which he is likely to be cross-examined.

(2) Take all records, and relevant reports that may have to be quoted in the box, e.g., original notes, autopsy report, photographs, X-rays, toxicology and blood grouping reports, copy of the death certificate, drawings or diagrams, special reports on swabs or smears, culture studies, serology and various receipts to prove the chain of custody of the items of evidence. The photographs are useful in the Court: to refresh memory of the findings, to establish the identity of the deceased, to explain the findings conveniently, and to provide true-to-life picture of the investigative findings.The records should be in chronological order, and the doctor should have full knowledge of the contents of his file.

(3) Do not discuss the case with anyone in the Court, except the lawyer by whom you were asked to testify.

(4) Be well dressed and modest.

(5) Stand up straight.

(6) Be relaxed and calm and not frightened or nervous.

(7) Never attempt to memorize. The law allows to refresh your memory from copies of reports already submitted or from case notes and similar records made at the time of examination. An expert may refresh his memory by reference to professional treatises (S.161, I.E.A.). A writing which is used to refresh the memory of a witness must be shown to the opposite party, if he requires it. Such party may cross-examine the witness thereupon (S.161, I.E.A.).

(8) Speak slowly, distinctly, and audibly so that the Judge can record your evidence. It is advisable to watch the pen of the Judge so that the Judge is able to record all the evidence, without asking the witness to pause.

(9) Look people in the eye when you speak, for it gives the impression of honesty.

(10) Speak with assurance. Be confident but not over-confident or arrogant.

(11) Use simple language, avoiding technical terms to the best of your ability. Practice this in advance.

(12) Avoid superlatives and exaggerations, e.g., very large bruise, frightful injury, savage blow, most agonizing pain, etc.

(13) Do not fumble in referring to case notes, records, etc. The less you fumble, the more the Court is likely to be impressed by you.

(14) Address the Judge by his proper title, such as “Sir” or “Your honor”.

(15) Avoid difference between your record and your testimony. If an error or slight contradiction has been made in the testimony, admit and correct it.

(16) Do not underestimate the medical knowledge of the lawyers.

(17) Be pleasant, polite and courteous to the lawyer. Appearance, professional manner, and general behavior are important.

(18) Do not avoid a question. Say I do not know, if it is so, for no one can be expected to know everything. It indicates honesty.

(19) Never become hostile, angry, rude or sarcastic during questioning.

(20) Do not lose your temper. An angry witness is often a poor witness, and the effectiveness of his testimony is diminished or destroyed.

(21) Defence lawyer may irritate the witness into anger by unfair questions, abuse and unfair remarks. The witness should remain calm and keep his temper. Do not argue, just disagree if you do not agree; disagree firmly and repeatedly.

(22) Don’t be too anxious to please or too eager to fight.

(23) Retain independence of your mind. Be honest, impartial, unbiased and truthful. A biased expert is a useless expert. Be frank to admit any points in favour of the accused if that is the truth. Speak only of facts which come within your personal knowledge.

(24) Do not alter your findings to what is said in statements to be the facts. The doctor should “tell it as it is”, and should not choose sides.

(25) Listen carefully to the questions. Do not hesitate to ask to have the question repeated, if you do not understand it. If still it is not clear, say so frankly, for the lawyer to reframe the question. Give yourself time to think.

(26) Avoid long discussion. Answer should be brief and precise and in the form of “Yes” or “No”. Never nod your head to indicate “Yes” or “No”. In many medical matters, the answer requires an explanation and the doctor should resist to answer with a simple ‘Yes’ or ‘No’. The witness is not bound simply to answer yes or no, but may qualify his answer if it is necessary for accuracy and completeness, even though the lawyer may try to demand a yes or no answer. The Court usually rules that the doctor may explain his reply.

(27) Consider all aspects of the question before answering it. Answer only what is asked.

(28) If you believe the question is unfair or that the lawyer is teasing you excessively, look at your lawyer before answering. If he fails to object, turn to the Judge and ask whether you should answer the question.

(29) Do not over emphasize replies to questions from the cross-examining lawyer.

(30) You may use an opportunity to insert a positive point that you have omitted during your chief-examination; but be careful not to provoke a new line to questioning.

(31) Watch for double question and questions that include an assumption of facts which have not been proven. The answer to each part of the double question may be different. This should be emphasized by the witness. He should also state that the assumed facts are not necessarily true.

(32) You are an authority in this particular case, as you have examined the patient or the dead body and have specific medical knowledge about it. What applies to many cases in general may not apply to this particular case.

(33) Express an opinion from your own knowledge and experience. Say, “In my opinion ….“ Do not use phrase such as “I think”, or “I imagine”. Be prepared to give reasons for your opinion if asked. Never express an opinion on the merits of the case.

(34) When the opinion relates to quantity or number, it should be stated within certain limits, unless an exact answer can be given, e.g., the age of an individual. Keep the opinions within the limits of reasonable medical certainty.

(35) Do not be drawn outside your particular field of competence. Avoid speaking on a subject in which you have little or no practical experience, e.g, pathologist is not the right person to give evidence on clinical problems or dispensing. A general practitioner is not qualified to give evidence on the pathology of a tumor or on blood group inheritance. In such cases, he should explain that this is not a matter in which he has particular knowledge, and that he is not qualified to answer it.

(36) When asked to comment upon the competence of a colleague, avoid any insulting remarks. If he is competent, say so but without superlatives. If you do not wish to make any statement, say that you have “no opinion”.

(37) An expert may adopt the published opinion of the writers on the subject as his own opinion. The published work need not be produced in the Court.

(38) When lawyer quotes a passage from a textbook, and asks the witness whether he agrees with it, the doctor must always take the precaution before answering, of reading the portion which is quoted to him and also of reading a paragraph before and after the quoted passage since it may be taken out of context, and he should satisfy himself that the edition of the book is recent and the views expressed by the author are current. There is no need to accept everything that is written; do not hesitate to disagree.

(39) Textbooks of established repute can be produced in evidence, even though the witness refuses to recognize the authority, or to acknowledge familiarity with its contents.

(40) A medical witness has no professional privilege, and therefore he must answer any question. He must first obtain a ruling from the Judge and if directed to answer, he must do so without further delay.

(41) Volunteering of information: Information should not be volunteered beyond that asked for in the question. The answer should also be limited to the expert’s knowledge. Volunteered information is often not well prepared, and is liable to cross-examination. As an expert witness, a medical practitioner may volunteer a statement, if he thinks that injustice will result if he fails to make the statement.