A coronial hearing into the Christchurch Mosque attacks has begun, but it's not a question of who is to blame.

Coroner Brigitte Windley is tasked with determining the circumstances of each of the 51 deaths - and addressing unanswered questions.

It follows a criminal prosecution and a Royal Commission of Inquiry.

Herald senior reporter Anna Leask has spent the day in court- and she says the Coroner is clear the responsibility rests on terrorist Brenton Tarrant.

She says this is about shining a light on what happened.

"Tarrant didn't go to trial because he pleaded guilty and the Royal Commission was done more privately, so there's a lot of the evidence that the families of the victims will only hear during this process."

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