Police may have contaminated handcuffs allegedly used on the girlfriend of missing UK backpacker Peter Falconio, defence barristers have suggested.
The killing allegedly took place on the remote Stuart Highway
Bradley Murdoch, 47, denies murdering Mr Falconio, from Huddersfield, and attacking Joanne Lees of Brighton.
His trial heard the cuffs - cable ties and tape - were photographed next to tape found at the home of the suspect.
But an officer investigating the 2001 disappearance in the outback said he was comparing possible similarities.
Mr Falconio, 28, disappeared after an alleged ambush in July 2001 on a road between Alice Springs and Darwin. His body has never been found.
The prosecution alleges Mr Murdoch shot Mr Falconio before threatening Miss Lees with a gun and tying her up with her hands behind her back, before she made her escape.
The Northern Territory Supreme Court in Darwin heard the handcuffs were photographed on a piece of paper about 1.5cm from a piece of tape found at Mr Murdoch's home.
Crime scene examiner Tim Sandry said the purpose was to make a comparison between the ends of the two pieces of tape.
Mr Sandry went on to deny having the cable ties over a two day period in February 2002 even though a police log recorded they were in his possession.
He told the jury: "The only explanation I can give is that possibly if I was going to do a further examination of the cable ties I would say, 'Can you release the cable ties to me and I will grab them later?'"
The court was also told a police log made no mention of the handcuffs after they were handed over to officers in Adelaide in October 2002.
Defence barrister Grant Algie asked Mr Sandry: "Is it because they were no longer reliable from a forensic science point of view?"
The judge, Chief Justice Brian Martin, intervened and said the officer was not in a position to answer the question, before adding: "You've made the point by your question".
On Thursday, the court heard the handcuffs were initially kept by police in the same room as the accused's property.
The defence also sought to draw attention to Miss Lees' evidence to the court.
She had told the jury her attacker's dog did not react as she screamed and struggled.
But in cross-examination by the defence, Mr Sandry told the court that when he first went to Mr Murdoch's properties in South Australia in October 2002, the defendant's dog was barking.
"When we first arrived I think there were some other dogs there as well and they came out as a pack, but once we got out he was wary of us, but he just went on his own way around the property."
In re-examination by prosecutor Anthony Elliott, however, Mr Sandry confirmed Mr Murdoch was not present when the dog was barking.
The trial was adjourned to allow crime scene examiner Ian Spilsbury to put photographic evidence in order.