Over five weeks of evidence, a multitude of theories about how the boy died were explored, including murder, neglect and drowning.
Yesterday was an emotional final day of Coroner Alexander Ho’s inquest into the 3-year-old’s death.
In 2019, Lachie was found 1.2km from his Gore home, face up in an oxidation pond.
Police quickly concluded he had drowned, but later confessed they "missed some steps" in the investigation.
Lachie’s father, Paul Jones, never believed his son drowned and suspected foul play.
Members of the public gallery wept as the court heard the lawyers involved sum up the case yesterday.
"It is hard to be asked to wait and to have faith in the process.
"No matter how Lachie came to be in the pond ... the death of a 3-year-old boy in a situation like this is a tragedy."
He reminded the court the inquest was not about proving anyone right or wrong, but rather finding out what happened.
"I will work as hard as I can ... to try and cast some light into the shadows [about] what happened to Lachie that day."
Counsel for police Robin Bates said the police admitted shortcomings in their investigation into Lachie’s death, but had since done everything they could to rectify those.
"No stone has been left unturned, as far as that can be done at this point.
"Everybody involved in this case would like to be able to turn back the clock to prior to Lachie’s death and prevent that."
The coroner would have to be careful when taking into account the evidence of retired United States major crime detective Karen Smith.
"Ms Smith’s evidence should come with a warning to read the label carefully.
"Ms Smith does not have a unique skill as she describes herself, but rather the time and motivation to review cases with the hope she will find something that others have missed."
But Mr Jones disagreed, and thought Ms Smith did a more thorough job than the police.
"My son idolised the police, but they have hugely let him down."
He thanked his supporters and legal team for their commitment to fighting for justice for Lachie.
Lachie’s death continued to affect him.
"I now spend all [of Lachie’s] Christmases and birthdays at a headstone."
Beatrix Woodhouse, counsel for Lachie’s mother Michelle Officer, said her client had to deal with untrue accusations of neglect and foul play.
"[Lachie] is and always will be sorely missed by his family, who are still grieving five years on."
There was no evidence of Ms Officer being neglectful and many witnesses said she was a loving, caring mother.
"This is a case where the evidence speaks for itself."
She urged the court to issue its findings as soon as possible to shut down "ongoing and unreasonable rumours or suspicions that have surrounded this case".
In a statement, Ms Officer said Lachie’s death continued to impact her.
"Our whole world has been shattered since Lachie’s passing."
She wanted to be able to grieve in private with her family.
Max Simpkins, counsel for Mr Jones, urged Coroner Ho to find Lachie’s cause of death was "undetermined" and recommend police should complete a "proper" investigation.
The evidence to support a diagnosis of drowning was "unconvincing".
If Lachie had walked near the ponds, the police dog should have been able to track his scent.
Police, medical professionals and the community had let down the vulnerable 3-year-old, Mr Simpkins said.
The case was not given the care and attention it deserved.
He placed weight on the condition of Lachie’s body at postmortem.
The lack of water in his lungs, his unmarked body and his face-up position in the water meant drowning was not a safe diagnosis.
Adam Holloway, counsel for the pathologist who completed Lachie’s autopsy, said there was little evidence that pointed to a diagnosis other than drowning.
"It is more likely than not that Lachlan drowned.
"Drowning is utterly consistent with what can be seen."
