The body of Ms Riedo, aged 17, was found in wasteland beside a pedestrian walkway known as The Line, close to the Lough Atalia area of Galway city.
She had arrived in Galway to study English three days earlier.
Gerald Barry, aged 28, of Rosan Glas, Rahoon, Galway, has pleaded not guilty to the murder of Manuela Riedo at Lough Atalia, Renmore, Galway on October 8, 2007.
He has pleaded guilty to stealing a camera and a mobile phone at the same place on the same date.
Mark Keady told Isobel Kennedy, prosecuting, that he was drinking with Barry at his house in Rosan Glas on October 17, 2007. He said that Barry asked him to buy a Sony Ericsson mobile phone and that he bought it for e30.
Mr Keady said he sold the phone on to John Enda Flaherty in Spiddal.
Mr Flaherty told the court that he bought the phone from Mr Keady for e20. He said that there were messages in the phone in a foreign language. He said that he gave the phone to his brother Robert.
Robert Flaherty told the court that he put his SIM card in the phone and noticed that there were a lot of messages written in a foreign language.
Mr Flaherty said he subsequently heard gardaí were looking for a phone and gave it to his father, John. John Flaherty told the court that he handed the phone over to the gardaí.
Arlette Riedo, Manuela’s mother, told the court that her daughter bought a Sony Ericsson mobile phone one week before she left for Galway.
Ms Riedo said that she went to Galway on January 1 last year and was shown a number of items by gardaí, including an Olympus camera. She told gardaí her daughter had received the camera as a gift from her uncle.
The court previously heard that gardaí found an Olympus camera between the mattress and the bed in the room Barry used at Rosan Glas.
Garda Geraldine Doherty said she received a printout of a photo that had been taken on the camera. She carried out a search to determine the location of the photo and said that she visited Millar’s Lane in the Rahoon area of Galway.
Gda Doherty took a number of photos from Millar’s Lane looking towards the Rahoon Road and Rosan Glas.
The location in the photo from Manuela’s camera and in the photo she had taken were the same.
Louise Barry told Dominic McGinn, prosecuting, that her brother, the accused man, was staying with her at Rosan Glas in October 2007.
Ms Barry said that she was shown CCTV footage by gardaí. She saw a man walking down a street wearing a red jacket and confirmed that she had seen her brother wearing a jacket similar to the one shown on the CCTV footage.
Dr Maureen Smith, of the Forensic Science Laboratory, told Ms Kennedy that she examined four swabs that gardaí had taken from the accused man.
Earlier, the court heard that a full single male DNA profile had been generated from the contents of the condom found “snagged in a bush” at the scene of the killing.
Dr Smith said that the profile of the condom’s contents matched the DNA profile of Barry.
She said the chances a person unrelated to Barry would have the same profile are one in a thousand million.
Dr Smith told the court that she generated a mixed DNA profile from the outside of the condom, which meant that there was DNA present for more than one person. The profile contained all the elements of DNA from both Barry and Ms Riedo.
Detective Garda Seamus Burke told the court that he interviewed Barry ten days after Manuela’s death.
He asked him: “Can you explain how your DNA was on the condom and that of the girl?”
Barry replied: “I can’t answer that question because I don’t know,” adding: “I haven’t worn a condom for the last five years so I don’t know how my DNA is in that condom.”
The trial resumes on Wednesday.