Expert Witnesses Play Vital Role in Determining Driver’s Duty of Care

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Lee v McGrath [2018] ACTSC 173, heard in early June, involved the Plaintiff being struck and receiving catastrophic injuries when he attempted to run across a busy highway. The driver of the vehicle failed to stop in time to avoid striking the Plaintiff, due to being distracted by the Plaintiff’s friends, who ran across the road shortly before the Plaintiff himself attempted to cross.


Elkaim J was required to consider:

  • Whether the Defendant breached her duty of care to the Plaintiff; and
  • Whether the Defendant’s negligence caused the harm.

Expert Evidence:

Both the Plaintiff and Defendant engaged expert witnesses to comment on whether the Defendant had an opportunity to brake. This issue went towards whether the Defendant had been negligent in failing to avoid the collision.

The biggest point of contention between the experts related to the point of impact. The Plaintiff’s expert witness wrote his report based on the assumption that the Plaintiff took a slightly different path across the road than his friends, giving the Defendant a greater opportunity to avoid the accident. The defendant’s expert witness wrote his report based on the assumption that the Plaintiff would have followed the same path across the road as his friends. The expert witnesses reached these conclusions based on different interpretations of the evidence at hand, including interviews with witnesses, and comments by the Defendant.

Elkraim J commented that the Plaintiff’s expert’s assumption had no evidentiary basis, while stating there was a “good deal of evidence” [1] to support the Defendant’s expert’s viewpoint. Elkraim J likewise preferred the Defendant’s expert witness’s view that the Plaintiff was likely to have been running “flat out”. [2] The question of causation ultimately came down to whether the collision occurred in the place assumed by the Plaintiff’s expert witness. Since this was not successfully proven, Elkraim J found that the accident was likely to have been unavoidable. Elkraim J commented that the expert reports in the case were only accepted into evidence on the basis that they would not “form part of the evidence unless otherwise proved”. [3] Since they were not proven, the Plaintiff’s expert witness did not have their evidence successfully accepted by the court.


Elkraim J rejected the Plaintiff’s argument that the Defendant’s reaction to the first two males crossing the road was negligent. He accepted that, although the Defendant was distracted, it was a reasonable reaction in the circumstances. His Honour, in his judgement, referred to the High Court judgement in Anikin v Sierra[4] namely that, expert evidence “…is only as helpful as the evidence and assumptions on which it is based.” [5] The assumptions which formed the basis of the Plaintiff’s expert witness report were rejected due to lack of any evidence supporting them.


This case demonstrates the importance of proving the assumptions which underpin an expert’s report. While there is no explicit ruling that expert evidence which fails to prove assumptions is inadmissible, the weight of the evidence is nonetheless significantly diminished. Thus, lawyers should be careful to weigh up the strength of their evidence before enlisting expensive expert comment.


[1] Lee v McGrath [2018] ACTSC 173 [76].

[2] Ibid [77].

[3] Ibid, 31.

[4] Anikin v Sierra [2004] HCA 64 [28].

[5] Ibid, 69.

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