The Canterbury Earthquakes Royal Commission has been examining the role played by a structural engineer in passing a building as safe to re-occupy following the first big quake in September last year.
The 7.1-magnitude quake on 4 September was followed by the fatal 6.3-magnitude quake on 22 February this year.
The bookshop on Riccarton Road collapsed in February quake, killing bricklayer Ross Bush who was parked outside.
The building was initially passed as being safe to reoccupy after a thorough assessment - known as a level two - by structural engineer David Elliott, three days after the September quake.
Mr Elliott said cracks in the facade were pre-existing and the front of the building did not show any signs it was leaning towards the road.
An inspector from the Christchurch City Council subsequently decided that the building required further inspection, due to concerns about cracks in the facade.
Mr Elliott directed the council to return the building's green sticker, despite failing to carry out a second thorough assessment, as he was required to do by the council.
Asked by the lawyer for the families of the earthquake victims on Wednesday if he would do the same thing again, Mr Elliott said he would not.