It’s a term used by police when speaking to the public about people involved in incidents, but what does 'known to police' actually mean?
Police in NSW have this week referenced the phrase when speaking about two separate stabbing incidents in Sydney.
After the , NSW Police Commissioner Karen Webb said attacker Joel Cauchi had "come to the notice of law enforcement" in NSW and Queensland for "mental health-related issues" but was not "known criminally".
Authorities said the 16-year-old boy alleged to have attacked Bishop Mar Mari Emmanuel at Christ the Good Shepherd Church in western Sydney on Monday night was also "known to police".
He was later , and was refused bail at a bedside hearing on Friday. The offence carries a maximum penalty of life imprisonment.
Asked on Tuesday, before the charge had been laid, about the nature of the boy's interactions with police, Commissioner Webb said: "He was not well known to police."
"I think the important thing here is that he was not known to us from a terrorism point of view, he was not on any terror watch list … this is the first time this individual has come to our attention in this manner."
What does the phrase 'known to police' mean?
There is no clear-cut definition of what 'known to police' means, according to Dr Michael Kennedy, policing studies professor at the University of New England and a former detective.
"Technically anyone — whether you’re a victim, witness or offender to a crime — would be interesting to police," he said.
He said all kinds of interactions can lead to someone catching the attention of authorities and it didn't necessarily mean the person had been charged with a crime.
"For instance, someone who buys a business previously owned by a criminal could have their details taken and saved," he said.
What does the phrase mean across the country?
While 'known to police' is a broad term, a majority of Australia's police departments said it is mostly used in the context of a crime or criminal behaviour.
SBS News contacted each police jurisdiction asking how their department defined the term.
A spokesperson for Tasmania Police said officers "may broadly refer to an alleged offender in a criminal matter as being 'known to police'."
NSW Police mostly use the expression in the "context of crime and police are referring to any previous adverse interactions," a spokesperson said.
Victoria Police gave a similar explanation, saying it commonly uses the term for "a person who has come to police attention for nefarious activities".
"These activities are generally in relation to crime or criminal behaviour, not being registered as missing or reporting a crime," a spokesperson said, noting "no official definition exists".
The Western Australia Police Force said the term is used publicly to confirm an offender's previous history with police. "This could be previous charges or associations with police," the spokesperson said, also noting "we do not use this term for witnesses".
Northern Territory Police echoed this, adding: "It would be unlikely a person who has previously witnessed a crime would ever be publicly described as known to police".
ACT Policing considers a person known to police if they have had significant contact.
"The interaction may or may not be criminal in nature," a spokesperson said. "This can include jobs involving checking on a person’s welfare and missing persons reports."
They noted that while a person for whom police have made checks for multiple mental health incidents would be considered 'known to police', they said it would be clarified that this was not for criminal matters.
Queensland Police also said the phrase generally refers to having an interaction with police, which "could be a street check, talking to police as a victim, witness or alleged offender".
"It doesn’t necessarily mean they have been charged with an offence in the past," the spokesperson said.
The Australian Federal Police (AFP) said the phrase is used sparingly.
"It is mainly used where police are trying to balance the need to be informative and transparent with the public, but where sub-judice (when a case is before a court) concerns may apply," a spokesperson said.
South Australia Police declined to comment.
How is information stored?
Some departments offered further details on how information relating to police interactions is stored, including in NSW, Queensland, Victoria, the ACT and the NT.
For example, NSW Police said a police computer database stores information relating to all interactions, including as a victim, suspect or charged with a crime. Victoria Police has "various databases" which may be used before referring to someone as 'known to police'.
ACT Policing referred to a "case management database" as a record of interactions, but stressed this is "not for tracking people, but for logging incidents police have been called to and/or are investigating".
On a federal level, the AFP spokesperson said it "uses the Police Realtime Online Management Information System (PROMIS), which is a searchable database".
According to Kennedy, databases create a permanent record that authorities can refer to.
"They [the police] can pop your name into the database, and any previous interactions or information will ping up," he said.
"Officers will have different ways of logging these interactions, meaning someone known in one state may not be in another. It’s a murky system."
Concerns over ‘harmful stereotyping’ and reputational damage
Barrister and criminal law researcher Dr Adam Booker said the vague nature of the phrase carried legal risks.
"In a public forum, the term invites speculation due to its flexible nature, and can lead to harmful stereotyping," he said.
"For instance, stating a First Nations person or Islamic person is 'known to police' can feed into unproductive criminalised narratives.
"In the example of someone identified as having mental health concerns, this can lead to demonising mental illnesses."
In Booker’s view, the phrase carries a risk of reputational damage.
"Saying someone is 'known to police' can delegitimise a suspect and could impact their right to a fair trial and presumption of innocence," he said.
"While explaining the police have had interactions with a person in the past can be useful information, using it publicly, in my view, does more damage than good."
However, Booker said it is part of human nature to be curious about alleged offenders and their pasts following highly publicised cases.
He referenced the Bondi Junction stabbing attack and public interest in identifying the offender, who was shot dead by a police officer, saying follow-up questions can include whether they have a history of misconduct.
"In that instance, police said to the media 'known to police' means some superficial interactions in Queensland and NSW related to the alleged offender’s mental health," he said, noting that "in some ways, [that] alleviates some of the concerns".
