The concept of a causal nexus in the context of a psychological injury claims refers to the requirement of establishing a direct link or connection between the employment and the development of the psychological injury.
It involves demonstrating that the injury occurred as a result of, or in the course of, employment-related factors.
Recent case law provides insights into how the causal nexus is evaluated in psychological injury claims. For example, in the case of Nizamdeen v University of New South Wales  NSWPIC 17, the Commission analysed the evidence to determine whether a causal connection existed between the worker’s employment and the psychological injury suffered.
The worker claimed to have sustained a psychological injury as a result of an incident on 30 August 2018, when he was arrested at work by the Australian Federal Police. The worker was accused of planning a terrorist attack based on entries found in a notebook. He was subsequently held in solitary confinement at Goulburn Correctional Centre for a month and subjected to lengthy interrogations. Ultimately, all charges against him were dropped.
Following his release, the worker lodged a claim for weekly and lump sum compensation, arguing that his employment played a significant role in the injury. He asserted that a co-worker had framed him by creating the incriminating notebook entries. Additionally, he contended that the arrest occurred during work hours and that he experienced humiliation and disgrace at the workplace.
The Commission considered various factors, such as the worker’s month-long imprisonment in a maximum-security prison, lengthy interrogations, media scrutiny, and feelings of racial profiling, to assess whether they were causally connected to the worker’s employment.
The Commission relied on medical evidence to support its finding that the worker had sustained a disease injury that developed over the month after his arrest. It determined that the worker’s psychological condition was causally linked to the circumstances surrounding his arrest and subsequent imprisonment. However, the Commission did not consider the arrest itself as the primary contributing factor required by the applicable legislation.
Decision & Analysis
Upon reviewing the evidence, the Commission determined that the worker had indeed sustained a disease injury that developed over the course of the month following his arrest. The member referred to the decision in NSW Police Force v Gurnhill  NSWWCCPD 12, in which it was indicated that in order for a psychological injury to be classified as a personal injury, it is necessary that the events complained of had a ‘physiological effect on the worker’, also described as a ‘sudden or identifiable physiological change’.
The medical evidence supported a causal link between the psychological condition and various factors, including the prolonged imprisonment in a maximum-security prison, the extensive interrogations during custody, the response of the police to the worker’s protestations of innocence, media attacks, and feelings of racial profiling.
While the Commission acknowledged that the arrest at work constituted a contributing factor to the development of the psychological injury, it did not establish the arrest as the primary contributing factor required by section 4(b) of the 1987 Workers Compensation Act.
Based on these findings, the Commission determined that the injury did not arise out of or occur in the course of the worker’s employment, as outlined in section 4(a) of the 1987 Act.
The Mercer v ANZ Banking Group Limited  NSWCA 138 case authority required the worker to establish that the cause of the injury was related to something he was doing for his employment, a causal test that was not satisfied in this instance due to the insufficient connection between the notebook, the co-worker, and the worker’s employment.
“This case underscores the significance of thoroughly examining the causal events when assessing workplace injuries. The establishment of a causal connection is determined by scrutinising the evidence that demonstrates a clear link. It is crucial for the worker to meet the burden of proof by presenting evidence that employment was the primary contributing factor, that the injury arose out of employment, and that it was a substantial contributing factor” – Trent Petherick.