In his closing arguments in the Court of Queen's Bench, Gilles Lemieux asked the jury why Bonnell would have led police to where 16-year-old Hilary Bonnell was buried if he killed her.
"If Curtis Bonnell had committed murder and tried to cover it up, why would he tell where the body was and ask for help to determine what happened?" he said.
Lemieux also dismissed a confession that his client made to police on Dec. 2, 2009, saying his client was telling police what they wanted to hear.
"The essence of the confession comes from the mouth of the police," he said.
Bonnell, 32, who has pleaded not guilty to first-degree murder, told his trial in Miramichi that the confession is false.
Bonnell testified that he woke up from a night of drinking and drugs on Sept. 5, 2009, to find his cousin dead next to him in his pickup truck, but he doesn't know how she died.
He said he panicked and buried her body in a remote wooded area in Tabusintac.
Crown attorney Bill Richards bluntly dismissed Bonnell's testimony.
"The Crown absolutely rejects the testimony of the accused," he said.
"I suggest it is preposterous."
He reminded the jury of a videotape confession they were shown where Bonnell tells police he sexually assaulted and killed his cousin.
On the video, Richards said, Bonnell tells police that at one point they fought and he hit Hilary across the face. Bonnell also says he sat on her and put his hand over her mouth.
Richards told the jury that a cut above Hilary's eye is consistent with that story.
But Richards said he believes the girl was knocked unconscious after she was struck and was driven to the woods, where she was killed.
That would be consistent, he said, with witnesses who saw both of them early on the morning of Sept. 5, 2009.
Richards said it also fits with the timing of a text messages sent by Hilary where she expressed her fear.
Bonnell was furious after a fight the previous day with his girlfriend, Richards said, and when it came to Hilary "he wasn't going to take 'No' from a 16-year-old."
Both the defence and the Crown finished their closing arguments on Thursday. Judge Fred Ferguson is expected to give his instructions to the jury on Friday.
Lemieux said there is no evidence in the autopsy report to show his client is guilty of murder.
A forensic pathologist who was called as a witness this week by the defence cast doubt on whether the girl was the victim of a homicide.
Dr. David Chiasson of the Hospital for Sick Children in Toronto said there was no trauma on the body and no cause of death identified in the toxicology report.
"I don't think we have enough information to make a homicide determination," he said.
Chiasson said Hilary could have died as a result of "positional asphyxia," which can happen when someone is intoxicated and they get in a slumped position that constricts their airway.
"It is a reasonable consideration in this situation," he said.