A probe into the death of two teenage Aboriginal girls who died near the NSW town of Bourke 34 years ago will finally resume after the State coroner gave the green light for the inquest.

Murrawarri and Kunja girl Mona, 16 at the time, and her Wangkumara cousin Jacinta Smith, 15, were found dead on the side of the road near a smashed ute on December 6, 1987.

Alexander Ian Grant, a 40-year-old non-Indigenous man was found uninjured with his arm across the nearly-naked body of Jacinta, who he was accused of sexually abusing.

Grant was aquitted at the time of drink driving resulting in death by an all-white jury.

A further charge of interfering with Jacinta's body was withdrawn.

The Australian revealed on Saturday the NSW Coroner would resume an inquest into the incident in the hope of finding answers for the cousins' family.

Jacinta's sister Kerrie Smith said the truth was needed to bring peace to the two girls' families.

"The police failed us all the way," she said.

"What happened to my sister was unforgivable and no-one has ever been held accountable.

"After 34 years, it's finally happening."

An inquest into the girls' deaths began nearly one year after the incident, but was suspended during the trial of the accused man and never resumed after the he was acquitted.

National Justice Project director George Newhouse said despite 34 years passing and the alleged perpetrator having died, it was not too late for accountability.

Mona's sister Fiona Smith said family had waited a long time for this moment.

"We're one step closer to finding out the truth and giving the girls closure," she said.

"It's hard to express the emotions we are feeling - happiness, sadness, love, it is overwhelming."

Grant died in 2017.