A man who raised questions over marks found on Robin Bain's thumb is calling for police to investigate potentially "significant" other markings.
Waikato man David Giles featured on TV3's Third Degree in June after he noticed the appearance of parallel lines on Mr Bain's right thumb.
It was alleged those marks were caused by Mr Bain loading a magazine into a .22 rifle shortly before his death, and led to police re-examining his fingerprints, and the gun used in the deaths of Mr Bain, his wife and three of his children.
His son, David, served more than 13 years in prison for the murder of his parents and three siblings before being acquitted in a 2009 retrial.
His defence team claims Robin Bain was the killer.