Frail grandmother is charged with murdering her young autistic son 50 years ago - as police begin digging under her neglected home in search of his body

An elderly woman has been charged with the murder of her autistic son five decades after his death. 

Maureen Anne Enright, 76, was arrested by homicide detectives at her Inala home, in Brisbane's south west, on Wednesday evening.   

Police will allege she murdered her son Peter John Enright who went missing sometime between 1968 and 1969 when he was aged three to four years old.

Homicide Detective Inspector Damien Hansen said Peter was born on June 17, 1965 and was one of 11 children to Maureen and Michael Enright, who passed away 2018.

Maureen Anne Enright , 76, was arrested by homicide detectives at her Inala home, in Brisbane's south west, on Wednesday evening

He said Peter was never reported missing but a murder investigation was launched following a tip-off to police in August.

Number 35 Polaris Street has been declared a crime scene and bone experts and forensic officers on Thursday started searching for Peter's remains at the Inala home where the family lived from 1966.

They have removed decades' of debris from under the house and are using ground-penetrating radar to scan beneath the earth. 

'Time causes problems but ... it's been a fascinating case,' Det Insp Hansen told reporters at the crime scene.   

'We're searching for a body. We're optimistic at this stage but that will be dependent on a lot of environmental factors ... time and acidity of soils.'

Homicide detectives are being assisted by investigators from the Child Trauma Unit and Inala Child Protection Unit to conduct inquiries as part of Operation Sierra Bobcat. 

Det Insp Hansen said Maureen had given police 'a number of versions' of events and all family members were being questioned about the disappearance.  

Ms Enright , 76,  appeared briefly before the Richlands Magistrates Court on Thursday morning

Number 35 Polaris Street  has been declared a crime scene and investigators have removed decades' of debris from under the house . The family have lived at the residence since 1966

He added that Peter's siblings had heard stories about him and police had gathered records of his existence, including a birth certificate.

'They were aware that Peter existed and they've given us versions for that,' he said.

'It's just a shocking thing that these things can happen but processes back in the 60s were obviously very different to what they are today.

'This is the first time I've come across something like this.' 

Detectives have urged anyone who lived on Polaris Street in Inala in the 1960s and 70s to contact police if they have information.  

'They were quite well known, some of the neighbours have been here for a long time too,' Det Insp Hansen said.  

The grandmother appeared briefly before the Richlands Magistrates Court on Thursday morning, where her case was adjourned for a committal mention on December 11, The Courier Mail reported. 

The frail elderly woman was accompanied by three women and required the assistance of a corrections officer to step into the dock. 

Forensic teams used ground penetrating radar to search for Peter's remains on Thursday

Police have until November 27 to tender their brief to the court and Ms Enright is not required to appear in court for the December hearing.  

Defence lawyer Jyoti Pant told reporters outside court her client would apply for bail in the Supreme Court.

'She is frail, she is vulnerable and so understandably her family is very concerned, she's concerned, we're concerned,' Ms Pant said.

'Our primary concern at the moment is to get her out on bail and back home with her family.

'We've just been provided material in relation to the charge and we'll be going through that later today.'