In 2020, gardaí upgraded her disappearance to a murder investigation after cold case detectives concluded that she "met her death through violent means".
[22] During an interview with the Irish Examiner on the 10th anniversary of Jo Jo's disappearance in 2005, Dullard's sister Mary Phelan insisted she knew the identity of the man who had murdered her, that this individual was the Garda's main suspect and he was the same person who had picked her up from the phone box in Moone at around 11.45pm on the night she disappeared.
Phelan also claimed that Gardaí had determined the man had driven from Offaly to Moone on the night in question around the same time Jo Jo was at the phone box, and that although he had given three contradictory statements to Gardaí about his exact movements, there was not enough probable cause for authorities to grant a search warrant for the man's farmland or car.
Phelan additionally claimed that during a confidential meeting with a senior Garda in 1996 she was informed that her sister Jo Jo had been abducted, raped, murdered, and then wrapped in plastic sheeting before being buried 10 feet underground in a hole dug by a mechanical digger, but the Garda himself expected the investigation to reach a dead end.
He further alleged that this suspect had a recent cut on his face around the time of her disappearance, which he did not seek medical attention for, that had since left an obvious scar.
Phelan also claimed that in April 1996, the Dullard family hired a private investigator to visit the suspect's farm under the ruse of being a lost tourist looking for directions, and that the suspect had a very prominent downward pointing scar on his face that looked like a recent wound caused by a fingernail.
The suspect, who was described as coming from a "well-known family", had been a longstanding person of interest in the investigation, according to media reports.
[34] A statement issued by the Garda Press Office declared that the area of land, located near Ballyhook Demesne townland outside Grangecon village on the Wicklow/Kildare border, would be subjected to excavation, technical and forensic examinations.
[35][36] A series of temporary no fly zones for unmanned drones were also declared over the search area by the Irish Aviation Authority.
[37][38][39][40] On the afternoon of 12 November 2024, the arrested man was released without charge from Garda custody, however forensic excavations continued at the search area on the Wicklow/Kildare border.
[42] According to media reports, the 2024 searches were focused on land where several witnesses had allegedly observed the arrested suspect digging and moving earth at times relevant to Garda investigations.
[17] Her disappearance was covered on Crimecall, an Irish television show which seeks public assistance in solving unsolved crimes, in 2020[22] and 2021.