Carlos Medina, of Torrance in LA County, has been charged with one count of murder and a special allegation that he used a firearm in connection to Bishop David O'Connell's murder on February 18.
Medina, 61, had previously pleaded not guilty to the charges at an arraignment hearing in March and faces up to 35 years in prison if convicted.
Los Angeles County District Attorney George Gascón laid out the forensic evidence against Medina at a preliminary hearing in Los Angeles on Thursday, August 10.
Investigators contend that Medina shot Bishop O'Connell multiple times with a .38 handgun while the Irish bishop was sleeping.
Bishop O'Connell, 69, was originally from Glanmire in Co Cork and was shot and killed in his residence in Hacienda Heights, around 30km east of downtown LA.
Medina was arrested on February 20, two days after the murder, following a standoff with LA police.
He allegedly made an initial confession to the murder before entering a not-guilty plea at an arraignment hearing in March.
Announcing the charges against Medina on February 22, Gascón described Bishop O'Connell's murder as a "brutal act of violence" against a man who "dedicated his life to making our neighborhoods safer, healthier, and always serving with love and compassion".
"Charging Mr. Medina will never repair the tremendous harm that was caused by this callous act, but it does take us one step closer to accountability," Gascón said in February.
Medina has been held at the notorious Twin Towers Correctional Facility in downtown Los Angeles since his arrest. His wife, who was Bishop O'Connell's housekeeper, has reportedly left the family home and is staying with friends.
Bishop O'Connell was affectionately remembered for his peacemaking efforts during the LA riots in 1992 after a jury acquitted four white police officers of charges connected with the severe beating of African-American man Rodney King.
The Irish-born bishop was also remembered for his work advocating for immigrants in the United States. More than 5,000 people attended his funeral in February.