The boy is one of a cluster of suicides involving 13 young indigenous people in the Kimberley being investigated at an inquest before WA Coroner Ros Fogliani in Broome this week after two weeks of earlier hearings in Perth.
He was charged in April 2015 by police officers for carrying a knife.
Senior Constable Daniel Fisher said his colleague Constable Matthew Hughes checked the boy's personal details but they did not know about this previous mental health problems.
The check should also have revealed that police took him to Broome Hospital four days earlier after he was found with alcohol and amphetamines in his system and trying to jump in front of cars, claiming that he wanted to kill himself.
Counsel assisting the coroner Philip Urquhart described his life as full of "struggles, pain, sorrow and neglect" from the moment he was born about half the weight of a healthy baby, likely with foetal alcohol spectrum disorder.
Yesterday the Inquest came under fire from the local Member for Kimberley Josie Farrer over a lack of language services at hearings.
"I feel that this inquest is a mockery to Aboriginal people, it's not going the way it should," she said in a letter.
"It is the right for people who don't have English as a first language to understand and be understood in their first languages ... it's policy."
Ms Fogliani said she was open to the use of language services if they were requested.
This week's hearings have also heard harrowing accounts of the suicides of two sisters, aged just 10 and 13, with the latter telling at least two people including a community elder about her plans to end her life in the days before but nothing was done.
Ms Fogliani and a team of lawyers are travelling to various Kimberley Aboriginal communities to speak to locals and see their living conditions, including Pandanus Park near Derby and One Mile in Broome.
Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.
