Deputy Police Commissioner Catherine Burn has revealed she has a setting on her mobile phone that automatically deletes text messages.
The revelations came in a budget estimates hearing on Thursday in which Commissioner Andrew Scipione said the police force has no policy or rules to stop officers from deleting work-related texts.
Ms Burn and Mr Scipione were grilled on the subject after Ms Burn deleted two potentially-important text messages from the night of the Lindt Cafe siege.
The deleted messages became the subject of intense scrutiny and criticism earlier this month as the inquest into the December 2014 siege examined possible failings by police during the 16-hour standoff.
In an unexpected and embarrassing twist, they were discovered in Ms Burn's email inbox on the morning of her second day in the witness box.
In several fiery exchanges with Mr Scipione on Thursday morning, Greens MP David Shoebridge asked whether the police should have a policy for not deleting work-related text messages.
"To the extent that they're records for policing work, they could well be essential," he asked.
Mr Scipione said officers must keep emails, under the State Records Act, but text messages are often private, short or inconsequential texts such as "see you in five minutes".
He said it wasn't always necessary to keep texts.
Mr Shoebridge suggested it was "woefully inadequate" for the police to have no policy on retaining text messages.
"Given the nature of the 21st century, often critical information is retained by way of text message. It may well be 'I will see you there in half an hour' but that may ultimately be critical information," he said.
Crucial police information is no doubt communicated in police text messages, but there is no policy to protect this information #nswpol— David Shoebridge (@ShoebridgeMLC) September 1, 2016
He then asked Ms Burn if she had a policy of routinely deleting text messages. She replied that she retains very few texts.
"Those that I retain are normally retained in hard copy or email format," she said.
Asked why she routinely deletes messages, she said one reason was that phones can be set to automatically delete text messages.
On an iPhone, it can be set to 30 days or one year.
"I don't keep emails either but there's a storage system that retains them," she said.
Mr Shoebridge suggested it was "grossly inadequate" for her to be routinely deleting text messages that may be essential.
The State Records Act does not include any reference to text messages.
Mr Scipione said he would look into whether they should be any guidance on the issue for police officers.
