The lawyer for murder suspect Bradley Murdoch has suggested that police investigating the Peter Falconio murder may have "set up" his client.
Joanne Lees and Peter Falconio were travelling across Australia
Barrister Grant Algie told the Northern Territory Supreme Court a number of factors "don't quite add up".
Mr Murdoch, 47, denies murdering the British backpacker and kidnapping and attacking his girlfriend, Joanne Lees.
Mr Algie said no blood was found in Mr Falconio's camper van and questioned why his body was never found.
"The absence of a body is a legitimate basis for serious concern when you are asked to return a verdict of murder," he said.
The prosecution alleges Mr Murdoch killed Mr Falconio after flagging down the couple's orange camper van on a remote stretch of the Stuart Highway, near Barrow Creek, about 200 miles north of Alice Springs on 14 July, 2001.
But Mr Algie suggested his client may have been "set up" by police.
Referring to Mr Murdoch's DNA which was found on a set of makeshift handcuffs, Mr Algie asked the jury: "Could they have been contaminated intentionally? Could it be to attempt, in the vernacular, a set up, a fit up?
"Is it possible that police or somebody who had access to these items could have fitted him up?"
The court also heard that Miss Lees used a piece of lip balm to try to ease the handcuffs off her wrists after escaping from her attacker's vehicle.
Its lid was found under a bush, but the lip balm itself and two pieces of black tape which Miss Lees said she bit off the handcuffs were not found until three months later in October when police returned to the scene on an "orientation" exercise - even though they were discovered in the same place.
Mr Algie said: "It's almost embarrassing to suggest that two crime scene officers in these circumstances would not have searched around the area."
The defence lawyer said the most obvious explanation was that "somebody has played around with the evidence to make it look like the lid and the tape was there when it was not.
"Or is it, as has been suggested in cross examination, that some kangaroo came along and took it away for a few months, and later brought it back - or perhaps it was a dingo?"
Mr Algie concluded: "It's yet another example of police manipulating the evidence to perhaps better the case to make it look a little better, with no harm done."
The lawyer also said there was "absolutely no rational explanation" why anyone would kill the backpacker in such a remote spot and then move the body.
"Why would you possibly pick up a dead body, complete with blood presumably, and put it in your car? Why would you do that? You would have to be nuts."
Had the events happened as the prosecution alleged, Mr Algie questioned why was there no blood in the couple's camper van, or a trail from the pool of Mr Falconio's blood found by the roadside, or drag marks.
The trial continues.