During the original trial, the court heard that Falconer had sent a text message to his step-sister Alice Meier, saying he was at the camper the night Kirwan disappeared, and that he dropped off some items there.
"There is a strange aspect of attending a property that's not yours and you're not in control of, presumably with a victim, knowing the occupants could return at any moment," said Seshagiri.
Crown prosecutor Tim O'Leary said the jury had viewed the texts and were capable of understanding what was factual in them, and what aspects they could interpret.
He said the judge didn't need to give further instruction on this evidence, other than what he provided in the charge to the jury.
"It was undisputed evidence," he said, referring to Falconer's presence at the camper.
O'Leary said the expert evidence provide by the toxicologists and other experts was subject to cross examination, and the jury was able to consider their validity.
"In this case, the jury was ... adequately, but not perfectly, instructed and the appellant had a fair trial and the jury was not misled about any factual issues," he said.
Chief Justice Michael MacDonald reserved judgment after hearing the arguments.
