The jury in the David Bain retrial has been told that footprints revealed under luminol testing may look complete, but are not necessarily so.
The complexities of using luminol testing to measure footprints is being debated in the High Court in Christchurch as David Bain's trial continued for the 27th day on Monday.
The Crown says David Bain, 37, killed his parents Robin and Margaret and siblings Arawa, Laniet and Stephen at the family's house in Dunedin on 20 June 1994.
The defence says Robin Bain killed the family present in the house before shooting himself.
Tests in the Bain home revealed several bloodied footprints near the bedrooms of Stephen, Laniet and Margaret Bain.
They were revealed using luminol, which shows up blood traces in the dark.
Two footprints were said to be complete, and measured 280 millimetres.
Forensic scientist Kevin Walshe, from Environmental Science and Research, told the jury on Monday that he completed similar tests. He found that a print may look complete, ie with toes and a heel, but was not always a complete print.
He based that on measuring prints made by a 300mm foot using luminol, and said even though the print showed the toes and a heel, the measurement of it was smaller than 300mm.
Mr Walshe told the jury his tests showed either David or Robin Bain could have made the footprints in the house.
The jury had already heard that David Bain's socks were found to have the soles bloodied, and droplets of blood from his siblings.
Robin Bain was found wearing socks and shoes and neither were bloodstained.