Murder charges to be laid over boy's death A top NSW homicide detective says the case of a seven-year-old boy allegedly murdered by his mother and her boyfriend is one of the most harrowing he's ever encountered. Police on Wednesday were preparing to charge a 29-year-old man and the boy's 25-year-old mother with murder, months after the child was found dead in an Oatley unit in south Sydney. NSW State Crime Command Homicide Squad Commander Mick Willing said the police case was linked to existing assault allegations levelled against the man. He described the case as among the most horrific he has ever dealt with. The boy was found dead in the early hours of May 21 after family members called paramedics, telling them the child had sustained head injuries after falling from a pogo stick the previous day. But detectives will allege the injuries were not accidental. A Sydney court has already heard the boy suffered "deplorable, prolonged abuse." The boy was allegedly reduced to begging for water from shocked campers at an Illawarra camping site two months before he was found dead, Parramatta Local Court was told at the man's September bail hearing. The man was originally charged with 25 offences, including assault, child neglect, taking action resulting in injury or sex abuse and producing child-abuse material. The mother is also expected to be charged with failing her parental responsibility to care for a child, common assault and producing child-abuse material. The mother, arrested in western Sydney on Wednesday, will front Fairfield Local Court within hours while the man is expected to appear via video link in Parramatta Local Court on Thursday. Detective Superintendent Willing defended the length of time taken to lay the new charges. The investigation has been complex. It has involved expert medical evidence and opinion, and we have gathered that," he said. As a father, he said, it was extremely distressing to think that a mother could murder her own child. A police statement of facts previously tendered in court said an autopsy showed three fractured ribs, a bruise in the shape of a fist, feet injuries and bruises to the boy's legs, back and buttocks that were inconsistent with normal childhood injury. The boy and his two younger siblings had been previously well cared for, but police allege that changed dramatically after the family moved early this year to the man's studio, which was windowless and had no toilet facilities. Several campers allegedly witnessed the boy being abused during the family's camping trip in March. He was seen sitting outside his tent one morning in cold weather, sobbing and wearing just a singlet and a towel around his waist, according to court documents. The boy later approached a camper in the amenities block and gestured to be lifted up towards the tap. Once placed under the tap, the boy "drank and drank," the camper later told police. Campers also allegedly witnessed the boy being beaten with a tree branch and forced to run laps until he fell face-down on the ground. One camper took a photo of the little boy that showed a lump between his eyes and another on his forehead. The campers contacted Wollongong police, who started an investigation. Two months later, the boy was dead.