A witness has told an inquest in Perth he heard his neighbour cursing and telling her young son to shut up in the hours before the toddler was found in a washing machine.

Daniel Dickerson lived next door to Kerry Murphy whose three-year-old son Sean died at their Hilton home in September 2010.

The inquest has heard Ms Murphy told police she was asleep and woke up in the middle of the day to find her son with his pet cat inside a combined washer dryer.

Mr Dickerson testified he heard Sean crying next door and later Ms Murphy yelling "shut up and stay in there until you quieten down."

He told the court his neighbour would sometimes growl at her son for days.

Mr Dickerson says he reported Ms Murphy to child protection authorities about a year before Sean died.

A representative of the Department for Child Protection said no record could be found of the complaint.

Mr Dickerson admitted to the court he was a regular cannabis user and he was upset with Ms Murphy because she had taken out a restraining order against his son.

But, he denied a claim from her lawyer that his evidence was a figment of his imagination.

Mr Dickerson told the inquest his neighbour later said to him she did not kill her son.

A police officer has also told the court he overheard Ms Murphy saying it was not her fault.

Constable Adam Clue attended the scene on the day of the boy's death and in a statement read to the court he said he heard Ms Murphy on the telephone saying she was being treated like a murder suspect.

He said he heard her say it was not her fault because she was asleep and that her son always did this and he was a little troublemaker.

Ms Murphy's mother, Dianne, told the inquest her daughter Kerry struggled at times with the pressures of being a parent.

In a statement given to police on the day of the death, Dianne Murphy said her daughter loved her son but could not always cope with her parental duties and at times had no patience.

She said she never saw her daughter mistreat Sean but on occasion she thought she was strict on him.

Mrs Murphy said at the time of her grandson's death she was estranged from her daughter but they had since reconciled.

An autopsy found the cause of Sean Murphy's death was consistent with entrapment.