Tips and traps for obtaining and relying on expert evidence

The value of taking the time to obtain good expert evidence cannot be underestimated.

Two recent decisions in the health law space have re-emphasised the need for lawyers to be aware of the importance and strategy of good (and not so good) expert evidence when litigating claims as well as preparing for hearing. The lessons to be learned from both cases are relevant to not only anyone practising in health law, but also to litigators more generally.

Busa v South Eastern Sydney Local Health District trading as Sydney Eye Hospital [2025] NSWSC 130

In this case, the plaintiff presented to Sydney Eye Hospital with a sore left eye, in the context of a complex eye history including, bilateral proliferative diabetic retinopathy and diabetic macular oedema. He underwent a tap and inject eye procedure and thereafter suffered loss of vision and ongoing pain. He sued the hospital for damages, alleged breach of duty of care on the stated basis that there had been too many taps on his eye

One of the issues for the Court to determine was whether the plaintiff’s initial presentation was consistent with suspicion for endophthalmitis (an infection requiring urgent medical attention due to the possibility of vision loss).

The plaintiff relied on an Italian expert ophthalmologist, Dr Pietro Morelli, who provided five reports. The Court noted that the first two reports were obtained by the plaintiff before his solicitors were retained to act on his behalf. No letters of instruction were sent requesting any of the five reports, even after the solicitors began acting for the plaintiff. Dr Morelli did not acknowledge the Expert Witness Code until his fourth report.

The Court decided not to admit the first two reports into evidence as:

• the Expert Witness Code was not acknowledged
• although Dr Morelli set out a history of what had occurred, this was largely informed by versions of events provided to him by the plaintiff and his sister rather than any of the relevant clinical records.

More generally, the Court found that it could not be established that Dr Morelli was able to provide an opinion on peer professional practice in Australia [1]. Dr Morelli did not practise, and had never practised, as a doctor and, more specifically, as an ophthalmic surgeon in Australia, which meant that he was in no position to make an appropriate judgment on the Sydney Eye Hospital’s ophthalmic surgeons.

The third report was largely based on an examination of the plaintiff undertaken by Dr Morelli as his treating doctor. The Court considered that this meant that he lacked the same objectivity of the medicolegal experts relied upon by the defendant. Again, this report did not acknowledge the Expert Witness Code and that very little opinion on what had occurred during the initial presentation was proffered. The report had been heavily redacted by those acting for the plaintiff. The Court held that this was also an indication that Dr Morelli was not acting as an expert to assist the Court impartially due to his treating relationship with the plaintiff.

Critically, the Court found Dr Morelli’s first duty was to his patient whereas the expert witness’s paramount duty is to assist the Court. Reference was made to Willoughby City Council v Transport Infrastructure Development Corporation (No 2) [2008] NSWLEC 238 in which Lloyd J stated[2], in the context of an expert report prepared by a local council officer:

The High Court decision in Pilmer v Duke Group Limited (2001) 207 CLR 165 at [82]-[83] supports the proposition that the existence of an ongoing or existing relationship between an expert witness and a party results in a breach of the necessary independence. That case involved an application of the stock exchange rules to the relationship between an auditor and an auditee. In my opinion, those rules and corporations law can have a general utility in deciding what is an independent report.

Another issue was that some of the conclusions reached by Dr Morelli in some of his reports were incongruent with conclusions he had reached in other reports.

The Court found for the defendant hospital.

Filmalter v Swenson [2025] QSC 32

In this case, the plaintiff attended an appointment with Dr Swenson, at which they discussed the potential finding of a urinary tract infection (UTI) based on plaintiff’s recent urine sample results. Based on those results and the plaintiff’s deteriorating symptoms, Dr Swenson prescribed Norfloxacin, an antibiotic.

The plaintiff said that she had a previous allergic reaction to an unknown antibiotic some years earlier, and had refused to take antibiotics since. She had informed Dr Swenson if this.

Less than a week after the prescription, the results of a urine culture test showed that there was no infection.

The plaintiff alleged that the Norfloxacin caused an allergic reaction, which in turn caused extreme photosensitivity and contributed to cerebral vasculitis and to a stroke she suffered 3 years later. The plaintiff sued Dr Swenson.

The Court stepped through the expert evidence relied on by the parties and made the following observations about the plaintiff’s medical expert:

• his opinions of findings on some issues were illogical, even when presented with the correct assumptions. Rather than make appropriate concessions, he effectively “doubled-down”;
• his report and evidence were tainted by bare ipse dixit or logical fallacy; and
• his conclusions were often contradicted by the clinical records, for example, whether or the plaintiff had a urinary tract infection, or whether or not the plaintiff had a temperature.

There was also an unfortunate incident which occurred when the plaintiff’s medical expert was giving oral evidence[3]:

When Dr Lynch was referred to his answer 7.3.1, Dr Lynch burst out laughing and could not contain his laughter, such that Court was adjourned to enable Dr Lynch to compose himself. The laughing was most inappropriate. It was, in my view, a very personal attack upon Dr Swenson which was most unwarranted. That is not the hallmark of an independent witness. Dr Lynch's response of uncontrollable laughter was also most unusual, but may have stemmed, as senior counsel for the plaintiff said, from an embarrassment as to the terms of the answer and the attack upon Dr Swenson. Although that was an inappropriate incident during the trial, it is not a matter, in my view, that is in any way of assistance in determining the preference of Dr Dickinson over Dr Lynch.

In finding for Dr Swenson, the Court determined that his expert ‘s opinions:

ought to be accepted over Dr Lynch's opinions, essentially because Dr Dickinson's opinions are logical and reasoned and based upon the correct assumptions. Dr Lynch's opinions are not based upon the correct assumptions, are not well-reasoned and as demonstrated above, Dr Lynch has used hindsight bias and circular reasoning. Dr Dickinson gave his evidence in a careful, logical and properly reasoned manner. He made multiple concessions, gave every appearance of being a completely independent and unbiased expert. I accept his opinions.

Checklist for briefing and obtaining expert evidence

These decisions are helpful in confirming some critical conditions that should be adhered to in obtaining/preparing expert evidence:

• Ensure your expert is exactly that – an expert who is unrelated to the plaintiff and can provide an impartial opinion.
• Ensure you provide your expert with properly drafted letters of instruction.
• Ensure you provide your expert with any applicable Expert Witness Code of Conduct and ask them to acknowledge it in their report.
• Ensure you have briefed your expert with the relevant primary materials (such as clinical records for health matters).
• If you seek further or supplementary reports from your expert, ensure that their opinions and conclusions are logical and consistent with earlier report/s, and if their opinion is different, that there is a rational and reasoned explanation for why their opinion may have changed.
• If relying on a peer professional defence[4], ensure your expert has practised or can comment on the practice in the relevant jurisdiction.