A Legal Treatise On Expert Evidence, 6th Edition by C. D. Field

It is widely recognized that experts have the authority to provide opinions in court based on their specialized knowledge of certain facts. Expert testimony, particularly on scientific principles that may be difficult for the average person to understand, can help clarify the issues at hand. Such opinions are admissible not only when scientific expertise is necessary but also when specialized experience and knowledge extend beyond that of an ordinary person.

A witness with specific skills or knowledge on a subject can offer an opinion, especially when the facts are complex enough that an untrained person might struggle to form an accurate judgment without expert assistance. This type of evidence is relevant when the expert's specialized understanding is likely to assist in uncovering the truth. However, it is important to note that medical expert testimony is considered opinion rather than fact. When there are alleged eyewitnesses to physical violence, the medical evidence presented by the prosecution serves mainly to support their testimony, showing that the injuries could have been inflicted in the manner described, but nothing more. The defense may use medical evidence to argue that the injuries could not have been caused as alleged, thereby questioning the credibility of the eyewitnesses.

A medical expert who conducts a postmortem examination provides factual testimony but also offers opinions on certain aspects of the case. The value of such testimony is not just to verify eyewitness accounts but also to provide independent evidence, as it may establish facts separate from other oral evidence. For example, if a person is shot at close range, the marks of tattooing found by the medical expert would indicate the proximity of the shot, independent of other opinions. Similarly, the nature of bone fractures or wound depth can reveal the type of weapon used. Courts generally respect the opinions of experts and only challenge them when the expert's conclusions are unreasonable.

An expert's written opinion cannot serve as evidence on its own; the expert must testify in court. Without the expert’s presence in the witness box, their written opinion cannot be treated as evidence under the law. For instance, a Xerox copy of a Forensic Science Laboratory report, rather than the original, cannot be relied upon to conclude that circumstantial evidence supports the victim's testimony.

Experts are not to be regarded as commissioners appointed by the court; they are simply witnesses brought in by the parties involved. Typically, witnesses provide testimony on facts within their direct knowledge, leaving the judge to form opinions and conclusions based on those facts. Someone with specialized experience is referred to as an "expert." Any deposition of a witness recorded and attested by a Magistrate in the presence of the accused can be used as evidence at trial, even if the witness is also called to testify in person.

Given the importance of this subject, the current revised and up-to-date edition offers a comprehensive overview of the Indian judiciary's stance on such critical matters. It includes the latest developments and issues in the relevant field, presented in a clear and accessible manner. Every effort has been made to enhance the book's usefulness, with thorough revisions and updates incorporating various rulings from the Supreme Court and High Courts.