Forensic consultant Peter Cropp has today agreed blood staining on one of David Bain's white sports socks could have been caused by contact with blood on the floor rather than by airborne blood.
Dr Cropp, a former ESR scientist, told the Bain retrial jury yesterday he believed blood staining on one of the socks was from droplets and was more likely to have dropped on the sock fabric from above, rather than the wearer having stepped on blood.
The blood could only have come from Bain's younger brother Stephen or Laniet, one of his sisters.
Both were shot dead in the family home along with another sister, Arawa and parents Robin and Margaret Bain, on June 20, 1994 and David Bain was subsequently charged with their murders and convicted.
The Crown says the blood on his socks shows Bain, not his father, was the person who shot the family and that the blood was deposited on his socks as a result of blood lost by Stephen during a violent struggle before he was killed.
Dr Cropp said yesterday he believed the blood had been airborne but under cross-examination by defence counsel Helen Cull QC today, Dr Cropp agreed that, if there had been experiments showing the staining could have occurred by blood being walked in, rather than from airborne drops of blood, he could not exclude that possibility.
However it would have had to be a relatively fresh blood stain with no signs of drying when it was walked on.
He had not carried out any experiments himself, Dr Cropp said.
And, asked by Ms Cull whether he would agree airborne spots would not give the type of stain seen on the sock, he said he could not agree without seeing the experiments but would accept the possibility the staining was caused by the sock walking on blood rather than from airborne blood.
Dr Cropp was unsure which foot the sock was from but, if it had been worn in the normal manner, the spots would have been somewhere on the bottom and edge of the sock.
He was the fourth of a group of forensic experts being called by the Crown in the retrial of 37-year-old David Cullen Bain for the 1994 murders of his parents and three siblings.
