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.
Mr Giles told the Otago Daily Times that while media attention focused around the lines on the thumb, "I think these other markings are interesting as well and should be included in the investigation".
An examination of higher resolution photographs revealed those other markings including faint circular marks on Mr Bain's thumb - similar in size to the hole in the magazine - while a mark on his palm were similar to the width of the magazine.
While stopping short of saying they were an exact match, Mr Giles wanted his findings investigated. His information had been collated and sent to police to assist their investigation.
"It's possible that they mean nothing, but if they match the magazine then I think that would be significant."
Mr Giles said he also noted smudging and staining in the photographs of Robin Bain's hands, and he wanted police to also investigate those discolourations.
"As the Bain case is still an unresolved murder case, I am hoping this evidence will be helpful for the police in their efforts to solve the case."
Mr Giles said it was his belief that "David Bain is innocent ... at least on balance of probabilities I figure he probably didn't do it".
While he believed the parallel lines were caused by the gun's magazine, "I will remain open-minded until the forensic report comes out".
Last month, police retested fingerprints taken from Robin Bain, and the gun was tested by firearms experts, with scientists from Environmental Science and Research present.
A police spokesman said they were still awaiting the results.