Patrick Quirke (50) of Breanshamore, Co Tipperary has pleaded not guilty to the murder of Mr Ryan - a part-time DJ going by the name Mr Moonlight.
Mr Ryan went missing on June 3, 2011 after leaving his girlfriend's home at about 6.30am and his body was found in an underground run-off tank on the farm leased by the accused at Fawnagown, Tipperary in April 2013.
The prosecution claims that Mr Quirke murdered Mr Ryan so he could rekindle an affair with Mary Lowry (52), the deceased's girlfriend.
Garda Gerry Canty, a crime scene examiner, told prosecution counsel Michael Bowman SC that he visited the scene at Fawnagowan the day after Mr Ryan's remains were found and photographed a number of items that were taken from the tank.
These included, he said, bone fragments, a lady's hair clip, cable ties, tubing, buttons and pipe covers. The items were placed in a tamper evident bag and marked as exhibits in the case.
Garda Canty told Lorcan Staines SC for the defence there was no discussion about those items when they were found and he said he didn't have any thoughts about them.
When Mr Staines asked if he or any gardai present were surprised that a lady's hair clip was found in the tank where Bobby Ryan's body lay the witness replied: "I wasn't surprised and no one else expressed surprise to me."
Garda Canty agreed that he made his first statement in relation to what he saw at Fawnagowan in November 2018, five and a half years after he visited the farm. He said he made the statement using notes he had written at the time.
He further accepted that he did not mention the hair clip in his statement or his written notes.
The witness also accepted that the garda exhibits chart stated that the tamper evident bag contained cable ties, a hair clip, tubing and pipe cover while the chart disclosed to the defence stated only that there were cable ties and pipe covers in the bag.
Under reexamination Garda Canty told Mr Bowman that he had nothing to do with retrieving, bagging, marking or charting the contents of the bag.
Detective Garda Sharon Langan of the ballistics section of the Garda Technical Bureau told Mr Bowman that she visited the farm at Fawnagowan on April 30, 2013.
When she looked into the tank she saw what she thought was a body lying face down in water or effluent. She watched as it was removed from the tank by firefighters wearing bio-hazard suits.
Once the body had been removed it was laid on a sheet of plastic and wrapped up. It was "fairly decomposed", she said, and she noted a gold watch but no clothes.
The following day she attended a post mortem carried out by Dr Khalid Jaber who handed her samples including muscle tissue, the watch, bone marrow, head hair, a maggot and a tooth. She bagged each of these so they could be delivered to forensic scientists for examination.
She also examined the deceased's Citroen van and agreed with Mr Staines that since Mr Ryan's disappearance the van had been used in an RTE Crimecall programme and was also returned to the deceased's son Robert Ryan Jnr.
As a result, she said she was not optimistic about finding relevant evidence from it.
She further told Mr Staines that she could remember a large concrete lid being removed from the tank by a JCB and she remembered seeing the lid crack.
She didn't make a note of the crack, she said, and didn't mention it in her statement.
Mr Staines asked her if the removal of the lid was a significant event on the day and the witness replied: "no".
Mr Staines said that everyone present knew that a body had been found in the tank and the decision was made to take the lid off in the hope that it would be done as efficiently as possible and with the least amount of destruction possible.
"So when it shattered it would have been to the forefront of the minds of those watching," he said.
The witness said she doesn't remember and agreed that it is not mentioned in her notes.
Mr Staines suggested there would have been dust and pieces breaking off, rocks and pebbles falling into the tank. He again asked if this was not a significant event that she would remember.
Det Garda Langan replied: "I'm sorry, I really don't."
The witness added that she was not aware if the deceased's arm came away during the efforts to retrieve him from the tank.
Counsel asked her if there was any conversation about bringing in a pathologist before removing the body and she agreed that it is best practice to do so and in an "ideal world all of that would fall in to place".
She said she was not making the decisions in this case but from her experience she knows that sometimes scientists are requested but are not available.
She added: "We carry on as best we can."
She said there was no urgency and nobody had said they had to get the body out of the tank quickly.
Under reexamination she told Mr Bowman that it would not be appropriate to engage with a body "in situ" in circumstances where there is a potential health and safety issue.
This was, she said, one such case.
She further noted that the firemen who entered the tank did so wearing bio-hazard suits.
The trial continues in front of the jury of six men and six women on Friday as Justice Eileen Creedon said she has matters to deal with in the jury's absence on Wednesday and Thursday.
Subscribe or register today to discover more from DonegalLive.ie
Buy the e-paper of the Donegal Democrat, Donegal People's Press, Donegal Post and Inish Times here for instant access to Donegal's premier news titles.
Keep up with the latest news from Donegal with our daily newsletter featuring the most important stories of the day delivered to your inbox every evening at 5pm.