Reward in Sydney acid murder investigation

The "horrendous" acid-attack murder of a homeless Sydney woman almost seven years ago has prompted authorities to offer a $500,000 reward for information about her death.

Monika Chetty, a 39-year-old mother of three, was found critically injured in bushland at West Hoxton, on the evening of January 3, 2014 and died 28 days later at Concord Hospital.

Ms Chetty - who was found with extensive acid burns to her face and body - had been estranged from her family since 2010 and was sleeping rough. Evidence suggests Ms Chetty was doused in acid between five and 10 days before she was found.

She repeatedly refused help from people while homeless and instead only sought cash, leading police at the time to believe she was under pressure to provide money to someone.

Police at the time also said Ms Chetty, who was a qualified nurse, deliberately misled them about the location of the attack to protect herself and her family from reprisal.

NSW Police Minister David Elliott on Monday announced a $500,000 reward for information on Ms Chetty's death, saying the incident had shocked the southwest Sydney community.

Detective Superintendent Adam Whyte said the investigation into Ms Chetty's death had slowly progressed over the past six years but now required help from the community.

He didn't rule out the possibility Ms Chetty knew her killer.

"What happened to Monika was horrendous and someone will have seen or heard or know something," Det Supt Whyte told reporters.

"It's a terrible situation whereby someone has sustained such a significant injury and may have gone some days (before) being able to get any help whatsoever.

"However Monika may have tried to conceal herself."

The $500,000 government reward is available to anyone who provides information that leads to the arrest and conviction of those responsible for Ms Chetty's death.

In September 2018 police searched a Fairfield pawn shop in relation to Ms Chetty's death, confiscating two computer hard drives and business records. Ms Chetty may have received calls before and after the attack from handsets that were then pawned at the shop.

Ms Chetty's son Daniel said the uncertainty surrounding his mother's death remained painful.

"It has been really hard not having my mum here for special occasions and milestones," he said in a statement on Monday.

"There has to be someone out there who has information that can help investigators - I urge them to come forward so we can find out why my mother was taken from us."