Former Northern Territory constable Zachary Rolfe shot the 19-year-old three times while on duty in the remote community of Yuendumu in November 2019 and was acquitted of murder in a five-week trial.
Mr Rolfe took the stand at an inquest into Mr Walker's death on Monday, faced with questions about his falsified police applications.
The former military soldier was convicted of theft in the internal military court for stealing tobacco from a colleague in 2012 during a drunken night with defence colleagues.
In 2011 he was also fined $300 for public nuisance with violent behaviour for his involvement in a Townsville brawl.
In 2016 he applied to several police forces in the NT, Queensland and Western Australia.
But he checked "no" on questions asking whether he had any previous altercations with police or was ever charged or convicted of any offences.
In March 2016, the Queensland Police integrity unit banned Mr Rolfe from re-applying for ten years because he had not disclosed the fine.
Mr Rolfe said it was an innocent mistake to not disclose his criminal history.
"I suggest to you that you deliberately didn't disclose that you had spoken to police about that incident," Counsel Assisting the coroner Peggy Dwyer said.
"No that's not correct... I didn't remember," he answered.
A week later, the then 24-year-old was interviewed by NT Police, his last preference for police placement, and divulged the 2011 Townsville incident.
"I told him about the event ... and I believe he laughed and said 'you'll fit in here'," Mr Rolfe said.
He also admitted he lied on the police drug checks by checking "no" to prior drug use when he had used marijuana as a teenager and MDMA as an adult.
"It was to give me the best chance of getting into the (police) at that time," he said.
The former NT Police constable was also asked about racist culture within NT Police, saying other officers had lied earlier in the inquest when they said racism was not pervasive in the force.
Mr Rolfe said racism was unacceptable but accepted in NT Police, used nearly daily and normalised.
He said the NT Police Territory Response Group, issued an annual award to its officers, using a derogatory name for Indigenous people.Â
NT Police lawyer Ian Freckleton told the court the matter was now being investigated.
Mr Rolfe reflected on racist text messages he sent, shown at the inquest in 2022, saying language he used to describe Indigenous people would have caused hurt to a number of people.
" That killed me, I'm sorry for that," he said.
Mr Rolfe's legal team has argued questions regarding eight use-of-force incidents, his police force application and some of the racist text messages should not be admissable.
Coroner Elisabeth Armitage's inquest into the death has been beset by delays. (Aaron Bunch/AAP PHOTOS)
The inquest resumed on Thursday, with the constable's former manager Sergeant Lee Bauwens telling the coroner Mr Rolfe's fatal shooting of the teenager was "appropriate policing".
Mr Rolfe has lost several challenges to avoid answering questions at the inquest, including asking the NT coroner to step aside due to perceived bias.
His evidence is set to take all week.
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