The boy and his six-year-old brother were burning white candles and incense sticks left in the hallway outside their flat when clothes the elderly woman hung out caught fire and the blaze spread to her flat.

The woman and a 34-year-old domestic helper suffered smoke inhalation - while the helper was rescued, the elder woman fell into a coma. She was pronounced dead at 9.29pm on Friday.

The boy, out on bail, is due to report back mid next month.

For under-14 convictions, barrister Albert Luk Wai-hung said courts need to consider whether there was intent while psychiatrists need to determine if mental health issues are involved, as well as a legal principle called doli incapax to determine whether a kid can tell right from wrong.

"The maximum sentence for manslaughter is life but it's hard to tell in this case," Luk said.