The case of Victorian man Robert Farquharson, twice convicted for murder for driving a car into a dam with his three sons inside, has paralysed author Helen Garner. But she can’t write about it. Not yet.

Garner, whose literary reputation is largely based on forensic and genre-bending explorations of legal cases, has sat in for much of Farquharson’s trials and intends to write a book on it. But she told a Melbourne audience last night that with the case not complete — he was found guilty after the 2005 deaths, won the right to a retrial, was found guilty on retrial, and is now appealing — she can’t craft the story. She tried to write, a process she described as hauling great shreds of seaweeds from her guts in the form of 70,000 words, which her sister described as boring and she has now junked.

So Garner is waiting. Drifting past the Victorian Supreme Court like a “melancholy little ghost”, as she told the packed NonfictioNow/Wheeler Centre audience last night. Peering wistfully into other trials.

She gave the Farquharson anecdote to illustrate a broader point: that a story does not already exist through having happened. Rather, it is created by the writer, and can only be created when the time is right for it. It is difficult to force the process.

Divine confirmation for this approach was delivered when Garner visited her rented office in Melbourne recently, having spent little time there as she struggled to write on her latest case. She found the plaster ceiling had collapsed onto her chair, and woke up the next morning feeling “inexplicably light-hearted” at this other-worldly reward for her procrastination.

Garner urged would-be non-fiction writers to be patient and porous, to be courageous in seeking and conducting interviews, to avoid taking a template into an interview, and to be poised to pounce upon the unexpected and diversionary revelation. She rued one such missed teaser in an interview with a ballet dancer years ago — yet also warned pragmatically that much digression, however interesting, may ultimately have to be set aside.

Garner, whose softly spoken ability to find the most apt and revealing word or phrase to bring a situation to life was as evident in her speech as in her writing, described “the eroticism of interviewing”, the charge of psychic energy between subject and interviewer.

“Into you floods this tremendous tidal wave of agony,” she said, which at times she had found difficult to manage, citing her 2004 non-fiction work Joe Cinque’s Consolation. The harrowing book deals with the murder of a young Canberra man by his girlfriend, who had informed others of her plan to kill him at a dinner party.

Garner said her interviews sometimes ended in “shocking intimacy” and “emotional violence”; she wondered if she had subconsciously tried to create boundaries after the fact. In The First Stone (her 1995 book which covers allegations of s-xual harassment made by young women at the University of Melbourne against a college master), Garner found she could not even remember the faces of people she had interviewed at length when she met them again — her mind had tweaked their appearances, giving them different hair or more make-up.

“It did unnerve me, it really threw me,” she said of the experience.

Garner dwelt on the value of incorporating unexpected writers’ tools in non-fiction, which she is celebrated for — imagery, associations, emblematic objects; analysis of the subject bordering on the psychoanalytic (or using the psychoanalyst’s techniques). Some criticise Garner’s use of techniques more commonly used in fiction to write about real-world events, but she staunchly defended the value of using a broad brush in order to create and shape a story, to contemplate, and to explore the philosophical and psychological dimensions of real-life events.