A walker came across the skeletal remains of Elaine O'Hara after following her dog into a wooded area and hearing a "scratching" noise, the trial of Graham Dwyer heard.
Magali Vergnet, a professional dog trainer, told the court she made the discovery in the Dublin Mountains on September 13, 2012.
Led through her evidence by Sean Guerin SC for the prosecution, she said her own dog, "Millie" was with her as she walked a number of other dogs.
Ms Vergnet had permission to walk dogs on a private track, which was inside a locked gate and owned by farmer Frank Doyle.
The court heard how Millie, a Cocker Spaniel/King Charles cross, brought her the leg bone of a deer one day before she went on holiday that August which she placed on cement blocks out of the small dog's reach.
Ms Vergnet also said she left a small plastic suitcase there with a long lead, like a horses's lead in it, before her holiday but when she returned the bag was there but the lead was missing.
Over the next few weeks her dog brought her another three bones, the court heard, which the French woman believed were animal remains and also left them on concrete blocks.
After she put the dogs into her car, she went looking for Millie in the wooded area behind the blocks.
She heard her dog and a "scratching noise or something like that".
She agreed with Mr Guerin that she followed a path some distance and saw bones and a blue tracksuit bottoms with a bulge.
"I rub it with my foot and it felt like a shoe," she said.
She carried on and found her dog, who had "two big bones with her".
She also saw an area where there was what she described as a greasy white material on the grass.
She was concerned that they were human remains because of the tracksuit.
Ms Vergnet called friends for advice and Mr Doyle, and they returned that afternoon and saw "what was obviously a jaw bone" and she realised they were human remains.
Mr Doyle called gardai at Tallaght who came to the scene and a second runner was found in grass nearby. Ms Vergnet also showed officers the blade of a knife which was stuck in the ground.
Mr Doyle, the landowner, told the jury he had 50 acres at Killakee - 30 in forestry and 20 in open grouse moor.
He said he got a call from Ms Vergnet on September 13, 2013. She told him she had found bones and was concerned. She told him about a runner and tracksuit bottoms and they returned with a friend. They went into a wooded area and noticed what looked like a lower jaw bone. Realising they might be human remains, Mr Doyle called the gardai.
Mr Doyle said there was another area around 200 yards away which he thought couples used.
Asked by Mr Guerin why he thought couples courted there, he said: "You do see condoms and lots of McDonald's bags where they have eaten as well."
He said in the hunting season around 2011 into 2012, he went into that area while shooting to see if an animal had been struck. He saw a "big sheet of plastic with some string, a bottle of vaseline, a stick with nails sticking out of it and bits of plastic".
In 2013, after the discovery of the bones, he brought a garda sergeant to that area and pointed it out.
Remy Farrell SC, for the defence, asked in cross-examination if he thought those items were "out of place" and if he thought there was something "untoward or of a sexual nature going on".
"It did strike me as a bit funny," he replied.