Expert Witnesses: When it All Goes Wrong

share on


It is undoubtable that expert witnesses are an invaluable tool in the legal industry. They provide the court and the jury with insights into technical areas of expertise, which, in turn, allows juries and judges to make informed decisions on the case at hand. However, expert witnesses bring their own challenges and risks which legal counsel must be aware of when utilising expert witnesses in the dispute resolution process. The strength of an expert witness can often be the deciding factor in tense litigation and can directly impact on a parties’ reputation in the eyes of the jury.

In this blog, we will consider various risks and pitfalls that expert witness pose drawing on domestic and international case examples.

Experts taking short cuts

Not all expert witnesses are full time, professional expert witnesses. Many are practicing professionals who juggle the demands of being an expert witness with their normal workload. As can be seen in the 2015 UK case of Van Oord UK Ltd and another v Allseas UK Ltd[1], this can have disastrous effects if it leads to the expert witness cutting corners and taking short cuts to finalise their report.

In Van Oord, the claimant’s expert witness was heavily criticised for both his expert witness report and his testimony. This criticism was based on the fact that the expert:

– failed to investigate claims made by Van Oord without giving reference to underlying documents associated with the matter;

– cut and pasted portions of the claimant’s evidence directly into his expert report;

– annexed documents to his expert report which he had not reviewed; and

– did not review witness statements from opposition witnesses.

An expert’s credentials & credibility

Under s79 of the Evidence Act 1995 (NSW) a person who has “specialised knowledge based on the person’s training, study or experience” is exempt from the prohibition on opinion evidence found in section 76 of the Act. For more information on what constitutes expert, as opposed to lay, opinion see our blog Expert Opinion or Common Knowledge.

As such, legal counsel should ensure that their chosen expert for a particular dispute holds the requisite qualifications to give evidence on a particular topic. As seen in our recent case study of Ibrahimi & Ors v Commonwealth of Australia (No 3)[2], the court is able to exclude expert witness evidence if the testifying expert provides evidence which goes beyond their area of expertise or fails to provide reasoning and methodology behind their evidence.

Legal counsel should also do their due diligence on their chosen expert to ensure that the expert has no skeletons lurking in the closet which could be brought up in cross examination and discredit both the witness and their testimony.

Experts in the court room

While a certain individual may have stellar credentials in their chosen field, their demeanour in the court room will have just as great, if not greater, influence on the court as their technical testimony. An unfavourable demeanour can arise as a result of various factors: an expert may be overly confident and as a result come across as arrogant, disrespectful, and condescending. On the other hand, a nervous and jittery expert witness, overwhelmed by the formality and technicality of the court room process, may not instill confidence in a jury, reducing the weight of their evidence. Other factors which may influence how a jury treats an expert witness’ evidence include their appearance (including choice of attire and hairstyle – a witness in a suit and tie is likely to present a more trustworthy and knowledgeable front than an expert in jeans and a tee shirt) and their tardiness (turning up to court late is unlikely to bode well with either the judge or the jury).

Legal counsel should attempt to prepare their expert witnesses as fully as possible for the trial process, briefing them on how to give their evidence in a clear, concise, and polite manner as well as how to respond to cross examination where they may feel under pressure. Clear advice as to the need to dress formally and arrive on time as an indicator of the expert’s respect to the court should also be given to an expert witness.

Errors in expert evidence

Experts are revered in the eyes of the law, with their opinion evidence, as noted above, being exempt from the strictly enforced prohibition on opinion evidence in the court room. However, what happens when this evidence is wrong? While errors in evidence may not be seen for many years, mistakes or incorrect evidence given by an expert witness can have grave consequences for parties, particularly in the criminal sphere. As we have seen in the Lindy Chamberlain case, where expert evidence used to convict Chamberlain of the murder of her young child was later found to be scientifically unsound, incorrect expert evidence can have a catastrophic impact on the outcome of the case and the liberty of the defendant.

In the recent US case of Adnan Syed (made famous by the podcast Serial and discussed in our blog posts on the case[3] in June 2016), expert witness testimony has been at the forefront of the appeal to acquit Syed after 17 years’ imprisonment. While Syed has, as of 2016, had his conviction overturned based on his lawyer’s failure to properly cross examine an expert witness on cell phone evidence which placed Syed at the scene of the crime, Syed remains in prison awaiting a new trial. The case brought to light significant issues with the expert testimony used to convict Syed, with investigations into the methods used to place him at the scene of the crime revealing the use of inappropriate methodology which produced incorrect results (see our former blog Expert Witnesses in the Media – Part 2 (Undisclosed), which delves into these issues in further detail).


Expert witnesses assist greatly in the operation of our legal system and can often provide evidence on which the case at hand hinges. However, legal counsel should be on high alert to avoid any of the potential expert witness disasters discussed above. Clear lines of communication between legal counsel and their expert witness, advance warning as to the nature and expectations of the court room, as well as ensuring that the expert is well across the Expert Witness Code of Conduct should assist in ensuring that the above examples do not become a reality.


[1]  [2015] EWHC 3074 (TCC)

[2] [2016] NSWSC 1438

[3] Expert Witnesses in the Media – Part 1 and Expert Witnesses in the Media – Part 2 (Undisclosed)

Your search for a winning expert stops here.