Katrina Bohnenkamp was last officially seen in October 2012, after moving around several foster carers and boarding houses throughout her childhood.

Her father, Maiko Bohnenkamp, told the inquest into her disappearance that he was unable to take care of his daughter, having dealt with active drug addiction for 35 years.

The night before she disappeared Katrina was at her father's Strathfield boarding house. Deputy State Coroner Carmel Forbes heard their final conversation was calm, before he passed out.

But senior counsel Philip Strickland disputes the claim, pointing to previous police recordings where Mr Bohnenkamp spoke about a final argument with Katrina over her use of ice and dalliances with older men.

Mr Strickland suggested Katrina's father had changed his story because he was worried his original account implicated him in the disappearance.

"She turns up on my doorstep, I'm a toxic junkie, I begged for help....and something's gone pear-shaped and you want to blame me," Mr Bohnenkamp told the inquest.

"Yes, I have arguments with my kids. Does it mean I go bury her in a backyard, no."

Ms Forbes heard how the troubled teen would turn up at her father's house all hours of the morning demanding money, before he would send her back to whichever carer she was supposed to be living with.

Mr Strickland questioned Mr Bohnenkamp about the inconsistencies in his statements over the years, which he said were due to drug addiction and intoxication.

He likened his life during addiction to "groundhog day" and that dates or specific events all blended into one.

At the time of Katrina's disappearance, Mr Bohnenkamp said he would regularly ingest a mixture of heroin, methadone and valium or Xanax, "enough to kill an elephant".

"I still need to know what happened to my daughter," he said.

"I was not a fit role model or parent, but I do love my children, that's why I wanted to stay away, I was living a toxic life not very good for kids.

"I still believe she's alive."

Mr Bohnenkamp also believes his daughter was hanging around a 40-year-old man who had inappropriate relations with her.

Katrina's stepbrother Rick Olden, who gave evidence from Bathurst Correctional Centre, said he returned to the Strathfield home from Tasmania about a week before Katrina disappeared.

The first time he saw Katrina she told him someone was shooting her up with a hard substance.

Olden said Mr Bohnenkamp could "snap" and recounted a number of physical fights he had with him, but that he'd never seen him act violently towards Katrina.

The inquest will continue on Tuesday.

Australian Associated Press