Hanratty, Kian's Dad, took Valium that night and passed out. Prosecutors say he knew McMillan was high and should've ensured Kian's safety.
McMillan later tested positive for heroin, valium and alcohol. Jurors hear she was incapable of care and showed "wilful indifference".
The prosecution say Kian's death was "not a tragic accident" but "an entirely preventable death".
More top news
The family of Robert Hart are grieving afresh today after his brother-in-law died trying to rescue his children from the sea.
Manchester United defender Marcos Rojo believes team-mate Angel di Maria is one of the best players in the world.
Widnes' top-eight Super League hopes have been dealt a major blow with the loss of skipper Kevin Brown for at least six weeks.