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Role of Expert Opinion in Judicial Proceedings

Discuss About The Psychological Expert Witness Testimony Judicial.

According to the rules of evidence in Australia, the standard for establishing a fact must be proved based on the balance of probabilities in case of civil proceedings. In case of criminal proceedings, facts must be proved beyond any reasonable doubt.  As per the evidentiary rules, information must be placed before a court for enabling the court to determine an issue. These rules usually influence how a party must prove his or her case[1]. Generally, in order a party must persuade the court of a fact, it is important that adequate evidence is adduced before the court. While adducing such evidence, the party must ensure how to adduce such evidence of the fact, whether such admissible is admissible, and how much significance is attached to the evidence adduced.

Such admissibility of evidence in any proceeding is subjected to compliance with the admissibility rule and the interpretation that is made regarding such evidence by the presiding judge. Amongst the type of evidences, expert evidence plays an essential role in any criminal and civil proceedings. Expert opinion is crucial as evidence as it is reasoned conclusion that has been derived from a specialized knowledge of the experts[2]. This essay entails the significance of expert opinions as crucial evidence and that they have more knowledge about the matter in issue than the court. Their opinion is considered as a crucial evidence as they possess specialized knowledge about the matter in issue, thus, forming a reliable source of evidence.

An expert opinion is always admissible as a reliable source of information in the court that can overturn any decision of the court. This is because they are qualified, experienced and skilled in their respective fields possessing adequate knowledge that is beyond the knowledge of the judge. For instances, in medical cases, medical experts are summoned to provide expert opinion about the matter in issue, if it involves any question related to the medical field. Similarly, in criminal proceedings, handwriting experts, chemists, forensic experts are called to adduce evidence as they possess sufficient knowledge in the respective fields and a judge does not possess this knowledge, as his knowledge is confined to legal knowledge and reasoning. Similarly in any matter that is in dispute, and it involves legal reasoning and knowledge, any expert opinion related to legal matter may not be admissible[3].  The opinion of experts is admissible only when it is necessary to establish factual assumptions and requires the experts to interpret their reasoning process which forms the rationale for such decision.

Admissibility of Expert Opinion as Evidence

However, the Commonwealth of Australia enacted the Uniform Evidence Legislation, which laid down a statutory framework regarding the admissibility of expert opinion as crucial evidence in the court. According to the legal framework, the admissibility of expert opinion necessitates that the opinion provided by the expert must be relevant to the case. In other words, if such opinion of the expert is to be accepted by the court, it must have a rational impact either directly or indirectly on the evaluation of the probability of the existence of a fact in issue within the legal proceedings[4]. Hence, it is essential that the expert is able to prove the factual basis or reasoning that is used to come to a conclusion otherwise the opinion provided by such experts shall not be rendered as relevant and shall not be admissible in the court of law. For instance, an expert opinion regarding slipperiness is based on the assumption of a wooden surface shall be considered as completely irrelevant when the evidence in the disputed matter unambiguously establishes that the plaintiff has slipped on a concrete floor.

Further, another instance when the expert opinion may not be admissible in the court when the trial judge exercises his discretionary power and determines that the ‘probative value’ of such opinion might be unfairly prejudicial or confusing/misleading or it might result or cause undue waste of time.  Under the common law, it has been stated that any opinion evidence provided by the experts shall be excluded unless the factual bases upon which the opinion is provided is established by other evidence[5]. In Makita case, the court established a ‘basis rule’ according to which the experts must provide facts, assumptions as well the reasoning process that contributes to the inference that the experts draw using its skills and expertise.

In order to make any expert opinions admissible to the court, it is mandatory that the expert provides a detailed explanation about how their specialized knowledge applies to the observed facts to establish the opinion submitted. For establishing this, the expert must establish a connection between specialized knowledge and opinion of the witness. The court usually considers the reliability of the expert witness based on the experience, training and education, memberships, affiliations, etc. Although the opinion of an expert is not binding upon the court, the duty of an expert witness is to provide the court with necessary information relating to its expertise to conclude, thus, enabling the court to form a judgment after perusal of such information[6].

Legal Framework for Admitting Expert Opinion

According to the knowledge and views of Catherine (2017), the experts play a better role and can produce correct evidence related to the case as he has the grasp of the subject matter in particular as compared to the judge. It was noticed and observed that the experts put all their effort by going through the matter of the case, summarizing the facts, details and assumptions of the case based on which the appropriate or suitable decisions will be taken by the Court. In case of any alterations in the details of the matter, the expert must make the suitable rectifications and produce the entire evidence to the Court. As per the opinion of Johnston (2017), the Court relies on the documents and reports that are produced by the witness experts because they are more knowledgeable when the scenario is linked with the case. Therefore, the witness experts can always provide clear evidence than what is being mentioned in the evidentiary rules[7].

The evidentiary value of an expert opinion depends on the fact upon which it is based as well as  on the validity of the process through which conclusion is drawn. The opinion of the experts is subjected to examination and cross-examination. However, since they possess more knowledge compared to the judge in the specific area that is in dispute, their opinions are reliable and considered valid, hence are admissible. Moreover, the significance of the opinion of an expert lies in the credibility of the expert and the relevant facts that supports the opinion of such experts. Now, since their facts are checked to ensure its accuracy, it implies that much emphasis is given on the data based on which the experts draw their conclusion[8]. Therefore, it can be stated that though their opinions are subjected to cross-examination, but experts should be able to provide evidence without going through the evidentiary rules unlike other witnesses solely because their expertise and skills forms a reliable sources and facilitates the court to achieve reasonable settlement instead of dragging the cases through court proceedings.

As per the Evidence Act 1995 and the Federal Court Rules 2011, it is essential to state that is vital to provide evidence without being caught by the evidentiary rules. This statement can be agreed upon based on a few facts. In specific issues when a party can preserve a specialist for the aim to produce his or her opinion on the aspect of a case. Such individuals are regarded to be the expert witnesses. Their qualification in the area they are working with also matters[9]. The expert witnesses have the right and power to provide necessary proof regarding a matter.

Factors Influencing Admissibility of Expert Opinion

An expert witness has a few duties that he has to carry out for producing impartial evidence in their particular area of expertise. In the opinion of Cockburn, Tina, and Bill Madden (2017), ­­­­ the witness experts cannot pass a judgment or conclude unless the documents have been produced in the Court. However, the rules of evidence in Australia is also evolving as observed in the case of Clark v Ryan. The duty of the expert is to assist the Court regarding any specific matter. The parties cannot retain the expert at that moment. The report of the experts is necessary as it explains and describes in detail the qualification and the material used while making the report.

As per the Common law rules, it can be observed and concluded that in regard to the qualification of the individuals as expert witnesses play the major role in helping out the Court with their reports made on their expertise. The witness experts have their expertise in this specific sphere and always help out in deciding upon a case[10]. The uncertainty of a case can be exclude the opinion that is related to an issue that is based on a few statements that have not been proved in the evidence especially in the criminal cases. The nature of the expert evidence gives a summary of the case. Every detail is mentioned in the report or the document that is sent to the Court for further decisions and judgments. Therefore, it can be concluded stating that the expert witnesses can always provides evidence that has clarity and can be used by the Court. Relying on the evidentiary rules is not beneficial since the expert witnesses will always produce better information and summary of the case. The Court has been relying on the witness experts regarding both civil and criminal issues of Australia as they make them knowledgeable about the issues and cases going on in the Court[11]. Thus, the concluding factor of this analysis is that it has been agreed that the witness experts produces clear and specific evidence without getting caught down by the evidentiary rules.

It is evident that experts are aware of the existing evidentiary rules than the Court however, it is important on their part to maintain accuracy and clarity while providing with the evidences. It has been observed in Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA[12] that in case the evidence has been provided by an expert opinion, it is important that it must be admissible and must be bounded with a specialized field of knowledge. It is worthwhile to mention here that there must be a presence of an identified aspect in the relevant field which requires the application of specified training and experience. In this regard, it is noteworthy to mention here that, with the implementation of constant training and experiences, witness can become an expert based on the experiences of the expert’s knowledge and observations.

Duty of Expert Witness

It is important that the opinion should be wholly and substantially based on the accepted and assumed facts of the however; it must be proved in a different way. The opinion must be established on the examination of proper scientific and intellectual basis before reaching a relevant conclusion. In the perspective of modern scholars, it is important to be aware of the fact that whether the opinion is wholly or substantially based on the specialized knowledge of the expert. In some cases it may be proved that the opinion explicit may not be as a result of the specialized knowledge of the expert. It was held in HG v R (1999) 197 CLR 414[13], that the inference, personal views in relation to the creditability of the plaintiff as well as the process of reasoning was applied outside the relevant field of expertise.

Since time immemorial, it has been difficult on the part of the Courts to determine matters relating to scientific and technological applications. It is evident that Courts are at the ability to determine matters relating to judicial proceedings. It is true that Judges are expert in dealing with matters involving legal application they may not have knowledge regarding the application of various scientific methods[14]. Therefore, it is noteworthy to mention here that in an ever-increasing number of crimes and legal disputes in a modern society, it has been difficult for the Judges to resolve the matters without the assistance and application of relevant scientific and technological experts[15]. It is worthwhile to mention here that for the purpose of determining the application of scientific and technological methods in legal disputes, expert opinion is essential. However, it has been difficult on the part of the Courts to determine the fact that whether expert opinion would prove to be beneficial in determining the presence of scientific and technological methods in legal disputes.

In this regard, it is worth mentioning that an expert witness possesses specialized knowledge in the relevant field which helps in identifying the relevant issues associated with the dispute with the application of scientific methods. However, the authority to decide that what kind of scientific and technological methods should be applied to the legal dispute in concern lies on the Courts. In short, the disputes regarding the admissibility of expert testimony lie upon the Courts.

It is essential that the opinion of the expert should not only be relevant but also reliable. In Dasreef Pty Ltd v Hawchar [2011] HCA 21[16], it was held that for the purpose of satisfying the reliability regarding the concerned matter, the opinion of the expert must be an outcome of scientific reasoning. However, the authority lies upon the Judge to determine the fact that whether the expert has reached to a perfect conclusion with the application of scientific methodology or not. In this regard, Section 79 of the Evidence Act 1995(NSW) has been applied by the Court which states that the opinion of the expert must be based upon the specialized knowledge and training in relation to the training, experience and area of study.

Evidentiary Value and Credibility of Expert Opinion

It was observed in CSX Transp., Inc. v. Whittler, (1991)[17], that the Court rightly applied the four-prong test for the admissibility of expert testimony. This is  for determining the fact that whether opinion of the expert will prove to be beneficial to the relevant matter, whether the nature of the witness can be considered as an expert, whether the opinion evidence can be applied to the evidence at trial. It further determined whether the nature of the evidence can be can be considered to be scientifically and technically relevant. In Makita (Australia) Pty Ltd v Sprowles [2001] the failure of the expert to reach the conclusions in relation to the case was highly criticized by the NSW Court. Therefore, it can be stated that it is important that the evidences of the expert must be clearly and accurately identified. Failure to brief the witness of the expert appropriately may result into the rejection of the expert’s evidence. It is evident that the role of the expert is to provide assistance to the Court in determining issues related to the matter in dispute. However, for this purpose an expert may require additional information and relevant documents supporting the case. In this regard, it is the duty of the Court to provide the expert with the relevant information[18]. It is worthwhile to refer here that the ultimate duty of an independent expert is bound towards the Court and to the parties in dispute[19]. Therefore, the Court is at the authority to provide the expert with the relevant information for the purpose of determining the case and the expert is at the duty to provide the Court with certain criteria for the purpose of evaluation of expert opinion.

The facts in the case point towards the negligence of the employers in failing to provide a safe means of access to the employees. Relating the facts of the case to the question of the topic whether expert evidence has more credibility and enforceability than the court, the aim is to weigh the two opinions[20]. The expert in the above mentioned case tendered their opinion regarding the slipperiness of the stairs that led to the fall and sued the employee for negligence claiming damages, the facts of the case point towards the fact that the plaintiff fell at her workplace and the result fall led to injuries. Professor Morton who has an expertise in investigating cases related to slipperiness came in as the witness and claimed that the fall was due to the slipperiness.

After the trial judge had held the defendant guilty of negligence, he appealed, wherein three judges namely Pristley, Powell and Heydon JJA that the trial judge made a mistake by not accepting that the defendant here had breached his duty of care held it. Even thought the expert opinion was given by Professor Morton, the trial court as well as the Court of Appeal failed to admit it as evidence because the findings of Professor Morton was based on a previous history of non slippery stairs. Heydon JA held in his findings that an expert while giving his opinion must furnish the trier with all the facts and since Morton had failed to do that, there was no tenability of his opinion in court. The opinion of the trial judge was due to the opinion of Professor Morton and owing to his opinion regarding the slipperiness of the stairs, the trial judge admitted that the plaintiff fell because of the slipperiness of the stairs and not due to any mistake of the plaintiff. The plaintiff had very briefly explained his fall stating that it was due to her foot going underneath her and as a result she lost balance.

Professor Morton had carried two types of tests to conclude the slipperiness of the stairs.- one on the stairs and the other on the shoe of the plaintiff. Thought he conducted rigorous experiments on the stairs and the shoes, the pimary objective of an expert opinion was not met, that is, the primary goal is to furnish opinion so as to help in evaluation of the expert’s conclusion. As was held in the case of Paric v John Holland Constructions Pty Ltd[21] and Bugg v Day[22], the expert’s opinion needs to have logical rationale to prove and corroborate the facts. Ramsay v Watson [01961] 108 CLR 642[23], the court held that the judiciary cannot keep on determining the probabilities on their own for themselves, and that it should be done by the expert.

The expert has to prove and explain the facts he had relied upon to come to the conclusion in fixing any liability. This is done to ensure that there no mistrials. The key word in understanding the admissibility of an expert opinion is “specialized knowledge”. Whenever an expert opinion is sought to be tendered as admissible in a court of law, it has to show that the expert has had specialized knowledge in that field. The expert also has to prove that by specialized, training and expertise, he has gained the knowledge and is qualified to conduct the examination. Whenever an expert is relying on any “fact” which is already assumed, in that case, the expert has to show the intellectual flow behind reaching the conclusion. If the expert fails to show the substantial research that has led to the final conclusion, the court cannot accept the opinion. For a court to accept an expert’s opinion, he has to have specialized knowledge.

Thought the evidentiary rules mandate that the expert follow certain guidelines that make their opinion more acceptable, it is imperative for the courts to accept the opinions of the experts because they have specialized knowledge in a field and have gained that through years of experience. The experts conduct various experiments and study the subject with the best of their knowledge and if evidentiary rules are applied by the court in accepting their opinion, the process will slow down and will lose the essence.

Courts and judges should base their judgements on the basis of the opinion of the experts.  It can be agreed that experts possesses greater knowledge regarding the scientific and technological facts associated with the matter is dispute more than the Courts. However, it is essential on the part of the Court to ensure that the experts are well instructed regarding the issues of the matter concerned in order to ensure care and diligence.


Anderson, John. Uniform evidence law. Leichhardt, NSW: Federation, 2016.

Brodsky, Stanley L., and Ekaterina Pivovarova. "The credibility of witnesses." The Witness Stand and Lawrence S. Wrightsman, Jr.. Springer, New York, NY, 2016. 41-52.

Bronstein, Daniel A. Law for the expert witness. CRC Press, 2016.

Bugg v Day [1949] 79 CLR 442.

Cockburn, Tina, and Bill Madden. "Expert witness immunity in Australia after Attwells v Jackson Lalic Lawyers: A smaller and less predictable shield?." Journal of Law and Medicine 24.3 (2017): 628-639.

Evidence Act, 1995

Hale, Sandra, et al. "The effect of interpreting modes on witness credibility assessments." Interpreting 19.1 (2017): 69-96.

Heydon, John Dyson, and Sir Rupert Cross. Cross on evidence. LexisNexis Australia, 2015.

Johnston, G. A. R. "Drug analogues and substantial similarity, views of an expert witness." Australian journal of forensic sciences 49.6 (2017): 626-636.

Kadish, Sanford H., Stephen J. Schulhofer, and Rachel E. Barkow. Criminal law and its processes: cases and materials. Wolters Kluwer Law & Business, 2016.

Keane, Adrian, and Paul McKeown. The modern law of evidence. Oxford University Press, USA, 2014.

Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305.

O'barr, William M. Linguistic evidence: Language, power, and strategy in the courtroom. Elsevier, 2014.

Paric v John Holland Constructions Pty Ltd [1984] 2 NSWLR 505.

Ramsay v Watson [01961] 108 CLR 642.

Robertson, Bernard, George A. Vignaux, and Charles EH Berger. Interpreting evidence: evaluating forensic science in the courtroom. John Wiley & Sons, 2016.

Shapiro, David L., et al. "Psychological expert witness testimony and judicial decision making trends." International journal of law and psychiatry 42 (2015): 149-153.

Skellern, Catherine Y. "Paediatricians in the courtroom: Becoming an expert witness." Journal of paediatrics and child health 53.5 (2017): 435-438.

Svider, Peter F., et al. "Expert witness testimony guidelines: identifying areas for improvement." Otolaryngology–Head and Neck Surgery 152.2 (2015): 207-210.

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