Police have arrested a fourth person over the death of New Zealand helicopter pilot and firefighter Ian Pullen.
Mr Pullen was in the Hunter helping the NSW Rural Fire Service prepare for bushfire season when his lifeless body was found on the side of a road at Glenridding, near Singleton, in the early hours of September 29, 2018.
Hunter Valley Police District officers on Wednesday charged a 27-year-old Ivy-Jean Ward at Singleton over the 43-year-old's death - she faces one count each of being an accessory after the fact to murder and acting intending to pervert the course of justice.
Magistrate Hugh Donnelly granted Ms Ward conditional bail in Singleton Local Court on Thursday.
She will face court again on January 28.
Mr Pullen's wife Vicki on Thursday morning praised the ongoing work of investigators.
"I can't thank the NSW Police enough for their determination," she told the Newcastle Herald.
The latest arrest comes after three other people were charged in recent weeks over Mr Pullen's alleged murder - the trio remains before the courts.
Detectives went public with their breakthrough last month, charging 29-year-old Singleton man Joshua Knight with murder, dangerous driving occasioning death and failing to stop after a vehicle's impact had caused a death.
A few days later, they charged 30-year-old Nicole Mason with murder.
Police allege the pair were in a ute being driven by Mr Knight when it hit Mr Pullen, before they left the scene, returned and struck the pilot to the head with an unspecified object.
Investigators believe Mr Pullen was still alive when the pair got back to the scene.
On Monday, investigators arrested 21-year-old Lilli-Jane Kaye Sales at a Whittingham home and charged her with being an accessory after the fact to murder.
She faced Muswellbrook Local Court on Monday, where she was granted conditional bail.
Ms Sales will face court again on January 28.
It came after a two-year investigation involving a special police strike force, multiple appeals for information and a $350,000 reward offered by the state government as detectives worked to solve the mystery surrounding Mr Pullen's untimely death.
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