Introduction

Many employees are aware of their entitlement to employees’ compensation if they encounter an accident at work and suffer from injury as a result. But what if an employee just collapses at work and the cause is not clearly identifiable? To what extent can medical study help establish causation in these circumstances?

In the case of Chiu Kwai Yuk v Lee Tak Wah trading as HATCO Exhibition Production Company & Others [2022] HKDC 59, the District Court (the “Court”) discussed the application of medical study of aetiology to causation in law in respect of non-traumatic accidents.

Facts

On 9 January 2016, the Deceased was employed for one day by the 1^st Respondent as a casual worker to carry out booth decoration at the Hong Kong Convention and Exhibition Centre. Unable to complete the work within the normal working hours of 9 a.m. to 6 p.m., the Deceased and other workers worked overtime on that day. At around 9:20 p.m., upon returning to work from a cigarette break, the Deceased drank some water and suddenly collapsed. The Deceased was certified dead at 10:51 p.m., the cause of which was found to be cardiac arrest from Acute Myocardial Infarction (“AMI”), more commonly known as a heart attack.

Issue

Section 5(1) of the Employees’ Compensation Ordinance (Cap. 282) provides that:

“…if in any employment, personal injury by accident arising out of and in the course of the employment is caused to an employee, his employer shall be liable to pay compensation in accordance with this Ordinance.”

The Applicant claimed employees’ compensation against the Respondents on behalf of herself and other family members of the Deceased, on the ground that the Deceased’s heart attack was triggered by long working hours, erratic working schedule and psychological stress.

The issue thus boils down to whether the Deceased’s AMI was caused by an accident, and whether the accident arose out of and in the course of the employment.

Causation in medicine and law

The Court noted the differences between causation in the medical study of aetiology and causation in law. The Court emphasized that causation in law is a matter for the judge and not for the medical experts. The legal test is whether it is shown on balance probabilities that the accident was a substantially contributing cause of the injury.

The Court explained that many of the non-traumatic accidents, including AMI in this case, are results of a chronic pathological process (coronary artery disease in this case) that have gone on for years cumulating on the one moment. The difficulty is to identify the triggering event which caused the injury when:

1.        there is no medical investigation test to identify the triggering event (if any), and

2.        there is an unpredictable period between the triggering event and symptoms appearing.

The aetiological risk factors might only reveal a statistical correlation with an increased incidence of the accident over a background level of incidence but not whether this particular case is a background incidence or not. The Court warned medical experts against selecting one of those risk factors as the cause when they could not produce strong enough medical evidence to support the legal issue of causation.

The Court’s findings

The Court considered the article of “Nonlinear associations between working hours and overworked related cerebrovascular and cardiovascular diseases (CCVD)” and applied the recognition criteria adopted in Japan and Taiwan, which define overtime as the hours worked in excess of the standard maximum monthly working hours in that jurisdiction. According to those criteria, the onset of a CCVD can be attributed to overwork, after excluding personal and other workplace risk factors, if an employee:

1.        worked 100 hours or more of overtime during the month prior to the event, or

2.        worked an average of 45 hours or more of overtime per month for 2-6 consecutive months prior to the event.

As the Deceased was employed as a casual worker for only one day, the Court concluded that the Deceased’s case would not have satisfied such criteria, As such, there is not enough evidence to support that the death of the Deceased has arisen out of his employment. The application was therefore dismissed by the Court.

Key takeaway

Resting its conclusion upon the specific facts of this case, the Court has not ruled out the possibility of an employees’ compensation claim based on overtime work. The approach taken by the Court has remarkable implications however:

1.        The medical study of aetiology has its limits in assisting the Court to determine causation in law.

2.        It is generally insufficient to merely adduce medical studies that support the aetiological risk factors of the accident.  

3.        Identifying the triggering event in non-traumatic accidents can be difficult and pose a major hurdle for the claimant.