An expert witness may be called to appear to testify in civil cases as well as in criminal cases (Walls, 1971). An expert witness is called upon to give evidence in court as someone who has expertise in the field that is currently being investigated or as a small part in a larger investigation. An expert witness may be specialised in a variety of different fields and may be called if their specialised area comes into question at court. The expert may hold expertise in a number of areas such as medicine, forensics, environmental issues and archaeology. It is the duty of the expert witness to give truthful and objective evidence and this duty overrides any other obligation to the person whom he receives his instructions and pay from.
An example which illustrates the use of an expert witness in a trial is the case of Sally Clark. Sir Roy Meadow was a well respected witness as he was a professor of paediatrics and child health at the hospital of St James’ university (R v Clark, 2000). Mr Meadow used his opinions to incorrectly illustrate the facts of Bayesian theory in the trial of Sally Clark in 1999. Mr Meadows testified for the prosecution and claimed that the probability of two children dying from sudden infant death syndrome (SIDS) in the same family is about one in seventy-three million (R v Clark, 2000). However, he did not take into account the possibility that an arbitrarily chosen woman would murder her children. The statistical probability of one in seventy-three million is extremely flawed as it assumes that each child from the same family that dies of SIDS is an independent statistic. Sir Roy Meadows is a prime example of how easily it is for expert witnesses to influence the decisions made by a judge and jury. The case of Sally Clark is not the only case to have been affected by Mr Meadow as his evidence was used during the cases of Angela Cannings, Donna Anthony and Trupti Patel (The Daily Mail, 2006). All of whom were wrongly convicted and it was only when Mr Meadow’s evidence was found to be ‘unsafe’ that their cases were eligible to appeal. The case of Sally Clark became known as the worst miscarriage of justice in the recent history of the English criminal justice system. On a more positive note, Sally’s case has highlighted the importance of disclosure in criminal case and allowed the opportunity for many miscarriages’s of justice to be overturned, however, the system does recognise that some guilty parties will use it as a way to escape a prison term.
In recent years, forensic science has developed into a cluster of scientific specialties dedicated to the investigation of legally relevant matters of fact (Jasanoff, 1998). Forensic Scientists are among those that can be called as expert witnesses by the court. They are there like all other experts, not only to provide an account of the facts, but to also offer an interpretation to the court of the facts (Rothwell, 2004). The expert witness will generally give the court information that will generally be expected to give evidence on anything that falls into his competence and is therefore not strictly known by the judge or jury (Walls, 1971). The forensic scientist will give a range of opinions in court and will state his reasons for any conclusions that he may have reached.
The police have access to any necessary forensic expertise mainly through the range of services offered by the Forensic Science Service (White, 2004). Any materials that are collected during the processing of a crime scene that may of evidential value to the police must be collected and sent for analysis ensuring each item is free of contamination and that continuity has been assured (White, 2004). The forensic scientists will investigate all pieces of evidence that they are presented with and perform the required tests. The results of these tests are then written up into case notes and these case notes will form the basis of the forensic scientist’s statement for use by the prosecution in court.
Forensic science is a crucial part of any crime investigation, whether the crime which has been committed is criminal or civil (Willmore, 1998). During criminal cases, scientists are likely to investigate matters of an extreme nature (blood spatter, explosions, hand writing and voice recognition) whereas in civil cases experts are used to demonstrate that a claim of damages is fair and reasonable by investigating any appropriate evidence.
In the majority of cases an expert witness statement is enough, however, during more serious cases, such as murder, the scientist involved must accompany their and testify in person (Willmore, 1998). The statement, along with any other documentary evidence, must be disclosed to the other party (either defence or prosecution) prior to the trial. The role of the forensic scientist as an expert witness is very important however they must remain impartial at all times in order to ensure that the evidence is ‘safe’.
A forensic expert may be called to appear to give evidence for either the prosecution or the defence (Walls, 1971). When a forensic expert is called to give evidence for the prosecution the defence will produce their own forensic expert to test the strength of the evidence. Regardless of whether they were called to testify for the prosecution or the defence, an expert witness of any speciality, must remain impartial and objective.
When called to the stand the expert witness may bring with them the statement that they have compiled so that they are able to specifically refer to it when answering questions. After taking an oath the examination will begin whereby their name and work experience will be given first. According to R v Clark (2000) a forensic scientist’s statement must give details of the expert’s qualifications, their experience, accreditation and details of any literature or any other material which the expert has relied upon in their evidence. Their statement aims to set the scene by giving all of the facts and instructions that are given to the expert which is material to any of the opinions expressed in the statement or upon which those opinions are based. The statement should make clear which, if any, of the facts stated are within the expert’s field of knowledge and it must declare who carried out any examination, measurement or test upon each piece of evidence within the statement (R v Clark, 2000).
They shall then be cross examined by the opposing side whereby the evidence given by the expert witness shall be scrutinised (Saferstein, 2001). It is likely that the opposing side will attack the accuracy of the results and the interpretations of the findings. It is crucial that when being cross examined the expert witness must remain calm and collected.
After cross examination has concluded the expert may be re-examined by the side that called them to the stand. It is not possible for new evidence to be introduced at this stage as everything should have been disclosed prior to the start of the trial. After the expert has finished giving evidence they are free to leave, however, if any new evidence comes to light the expert is supposed to statement the new findings to the appropriate body.
The statement of an expert witness is a crucial document which represents the culmination of the labour that had been expended during the conduct of a criminal investigation. Many factors must be taken into account when preparing the statement for court, such as, the need for the statement to be written in comprehensive manner whereby those people who have no scientific background, such as the police, lawyers, jury and the judges, are able to understand all of the matters relating to the evidence.
Forensic scientists are often asked to match glass found on suspects clothes with glass found at the scene of a crime (Jackson and Jackson, 2004). Various uncertainties arise out of this process, such as the selection of which samples to test or what interpretations to make from any results that may show a match within the limits of experimental uncertainty. The forensic scientist assesses the likelihood of the match being coincidental by comparing the glass with a similar kind that has been present in previous cases. During a trial, even though the defence and the prosecution understand these uncertainties, they will be relying upon the expert witness to communicate their uncertainties to the jury (Jackson and Jackson, 2004). When doing so they need to ensure that they do this without misunderstanding or confusing individual jury members. Such misunderstandings are likely to cause a miscarriage of justice as demonstrated in the case of Sally Clark.
The legal system seeks to limit the amount of evidence which may be presented before the court (Willmore, 1998). There are many reasons why the law sets such limitations including cost, time and the complexity of cases. On a whole the legal system maintains that limitations that need to be set in order to structure the court into a complex enough form that is manageable.
In conclusion, criminal investigations may not rely upon the testimonies of expert witnesses, however, they are crucial to the how the judge and jury perceive the evidence that they give. Sir Roy Meadow made a critical error in the statistical evidence he made during the trial of Sally Clark.
References
Jackson, A.R.W., and Jackson, J.M. (2004) Forensic Science. Harlow, UK: Pearson Prentice Hall.
Jasanoff, S. (1998) Expert Games in Silicone Gel Breast Implant Litigation. In Freeman, M., and Reece, H. (eds) Science in court. Aldershot, England: Dartmouth Publishing Company Limited.
Rothwell, T. (2004) Presentation of Expert Forensic Evidence. In P.C White (ed) Crime Scene to Court: The essentials of Forensic Science. Cambridge, UK: The Royal Society of Chemistry.
R v Clark (2000) EWCA Crim 54.
Saferstein, R. (2001) Criminalists: An introduction to Forensic Science. (7th ed) New Jersey: Prentice Hall.
The Daily Mail (2006) Disappointed and Disheartened. (Internet) Available From: . Accessed 19.04.08.
Walls, H. (1971) ‘What is reasonable doubt? A forensic scientists look at the law’, Criminal Law Revire 458.
White, P.C. (ed) Crime Scene to Court: The essentials of Forensic Science (2nd ed). Cambridge, UK: The Royal Society of Chemistry.
Willmore, C. (1998) Codes of Practise. In Freeman, M., and Reece, H. (eds) Science in court. Aldershot, UK: Dartmouth Publishing Company Limited.
