Former Olympic swimmer Todd Pearson remembers his toddler son Zac being "happy as Larry" as he went to bed on a seemingly uneventful night in September 2009.
But the 22-month-old would never wake up, dying unexpectedly in his sleep in every parent's worst nightmare.
A coronial inquiry would later find he died of an overwhelming infection.
Mr Pearson and his wife Alisa would later comb through minute details of the days before his death for any sign that something was amiss, but always came up blank.
"We remember he was even playing with us on the night before we put him to sleep, so there wasn't any sign that would concern us," Mr Pearson said.
"But it must have been such an overwhelming infection that three hours later he was gone."
Their experience has prompted them to use a legacy fund set up in their son's name to support an emerging area of medical research that goes beyond the focus on sudden infant death syndrome.
While SIDS refers to deaths in babies up to the age of 12 months, research is looking at sudden unexpected deaths in children, or SUDC, which covers deaths in children aged one to 16.
These deaths are rare and mostly occur in children under six. While the cause is normally evident, often an accident or infection, in about 5 to 10 per cent of cases the reason is unknown.
SIDS and Kids WA, in association with Zac's legacy fund, is using a research bursary to fund work by University of WA medical student Stacey Prystupa under the supervision of forensic pathologist Jodi White. The research will re- examine cases of children who died suddenly and unexpectedly in WA between 2001 and 2010.
Dr White said research was vital to help understand the reasons children died unexpectedly so other deaths could be prevented.
"The research will involve taking a retrospective review of children aged one to 16 whose cause of death was not found despite a complete post-mortem examination," Dr White said.
SIDS and Kids WA chief executive Shauna Gaebler said it could help comfort bereaved families.
For more information about SUDC, call 9474 3544.