Why is a coroner sometimes involved?

Some circumstances require the registrar to report a death to the coroner before it can be registered. Examples of this include:

where the cause of death is unknown
where the cause of death is believed to be unnatural or suspicious
where the death happened during an operation or before recovery from an anaesthetic
where the death is due to industrial disease or industrial poisoning.

The coroner must then decide whether there should be further investigation into the death - and the registrar cannot register the death until the coroner notifies him / her of their decision.