Dr Peter Cropp, now an independent forensic scientist, who was previously employed by the ESR in Christchurch, also said blood found on a heavily stained pair of white cotton gloves in Stephen Bain's bedroom came from the same source, Stephen or Laniet.
David Cullen Bain, now aged 37, is charged with murdering his siblings, 14-year-old Stephen, 18-year-old Laniet and 19-year-old Arawa, as well as his parents, Robin and Margaret Bain, all of who were shot to death in their Dunedin home on June 20, 1994.
Bain denies the allegations and is on trial before Justice Graham Panckhurst and a jury.
The trial is his second on the five charges.
He was convicted at the end of his first trial in 1995 and served 12 years of a 16-year non-parole life sentence before the Privy Council decided two years ago the case should be heard again.
The Crown case is that David Bain, then a 22-year-old student, shot his family and tried to make it look like his father was responsible.
But the defence says Robin Bain shot his wife and three of his children, then committed suicide.
The defence contend that Robin Bain did what he did because he was suffering from serious depression and was also about to be exposed by Laniet for committing incest.
During the past few days, the jury has heard scientific evidence about the examining and testing of items and surfaces at the various crime scenes in the Every St house and much of yesterday's evidence related to blood taken from the murder weapon, a .22 Winchester rifle, and from items of clothing.
Dr Cropp said he examined a pair of socks labelled as belonging to David Bain and found droplets of blood on one of them.
He identified the blood as human and as coming from Stephen or Laniet.
He could make that finding as a result of blood-grouping tests he carried out on blood samples from each of the six family members, he told the court.
The parents had different blood groups from the four children, who all had some common characteristics, although he could not distinguish between Laniet and Stephen, Dr Cropp said.
A blood sample taken from the rifle could have come from Stephen, Laniet or David, but not from the other three members of the family, and blood on the front of the black shorts David Bain was wearing on June 20 could have come from Margaret, Arawa, Laniet or Stephen Bain, but not from David or his father.
The witness said he examined the extensively bloodstained T-shirt removed from Stephen Bain's body and testing of the blood showed it could have come only from Stephen or Laniet.
Some patterns of blood-staining on the shirt indicated blood had been transferred from an already blood-marked surface with an open-weave pattern.
Blood he tested from the clothing of Robin Bain was all Robin Bain's blood, Dr Cropp told the court.
Earlier, Nigel Hall, formerly manager of the Victorian Police Forensic Services Centre, said he took 13 samples for testing from the rifle and used a particular test to establish whether any human blood was present.
On 12 of the 13 samples, no human blood was detected, although that did not necessarily mean no blood was there.
It simply meant the test was not sensitive enough.
With the 13th sample, taken from the inside of the sight mounted on the silencer, the presence of human blood was confirmed.
Forensic scientist Stephen Gutowski, of the Victorian Police crime scene division, gave evidence of receiving several items and samples relating to the Bain case in March 1995.
These included David Bain's black shorts, cards with dried bloodstains from the Bain family members, a rifle and two small pieces of skin.
In 1997, he also received two heavily bloodstained white cotton gloves from Bain supporter Joe Karam.
He extracted DNA from the six reference bloodstains and from the black shorts and found it was all the same type, Mr Gutowski said.
He then carried out further "typing" which told him the four siblings all had the same DNA, but the parents were different, although strands of their DNA had been passed to the children.
His analysis of two small pieces of skin found in Stephen's bedroom told him they could have come from any of the four siblings, but not from either parent.
And Mr Gutowski's evidence was his testing of the blood from the cotton gloves and from the rifle sight showed it could only have come from Stephen Bain.
It could not have come from anyone else, he said.
