After filing the charges, police took Dontugan to Camp Crame in Quezon City, where he was presented to media by Philippine National Police chief Director General Oscar Calderon.
Among the evidence submitted by police against Dontugan, 24, was a signed affidavit in which he claimed to have killed Campbell in a fit of rage when she accidentally bumped into him as he was fuming over a neighborhood spat.
Police submitted at least 15 other pieces of evidence, among them Campbell’s personal belongings  a digital camera and two eyeglasses, as well as a rice pestle and two pairs of denim pants.
Police said they decided to elevate the case from robbery with homicide to murder due to Dontugan’s act of burying Campbell’s remains in a shallow grave.
Investigators initially thought of filing homicide charges against Dontugan, believing that Campbell’s killing was not premeditated.
Cordillera Administrative Region police commander Chief Superintendent Raul Gonzales said although the killing does not appear to be premeditated, Dontugan is still liable for murder because he tried to conceal the crime.
"If he did not plan to kill her, he should have stopped when she was already wounded and down," he said. "But no, he hit her repeatedly on the head until she died."
Dontugan, a native of Benguet who now resides in Banaue with his wife, had admitted hitting Campbell on the head with a blunt object.
Ifugao Provincial Prosecutor Marvin Ngayawan said he and other prosecutors would evaluate the evidence submitted by police, including the statements of at least six witnesses, then decide whether Dontugan would be charged in court with murder or homicide.
Dontugan appeared haggard when Calderon presented him to media yesterday.
He was wearing a gray jacket over a red t-shirt, denim pants, and a pair of rubber slippers.
He had not changed clothes since he surrendered to police last Friday.
"I am very pleased to announce some significant developments in our ongoing investigation of the murder of Miss Campbell," Calderon said.
"The surrender last week of Dontugan is an encouraging development in the investigation. And we acknowledge the efforts of Dontugan’s mother and an uncle who facilitated the surrender."
Calderon said based on Dontugan’s confession and statement before the Ifugao police in the presence of a lawyer from the Public Attorney’s Office, Maribas Lubiton-Habawel, police recovered his bloodied sleeveless shirt and baseball cap, some personal belongings of Campbell, and a bloodied piece of firewood.
"But we are not taking his statements hook, line and sinker," Calderon said. "We want to cross-check his statements with evidence and the findings of our own investigation."
Calderon said Dontugan’s confession would somehow relieve apprehension of some tourists in visiting the picturesque rice terraces in Batad, Banaue for fear of suffering the fate of Campbell.
"His confession indicated that the incident was an isolated case," Calderon said.
Calderon has instructed Cordillera police to establish a tourist assistance center in Batad. – With Cecille Suerte Felipe, AP