Emma Hart and Lewis Dangerfield were found hours apart
A woman suspected of killing her son before killing herself left notes for his father asking if he really thought she would let him bring up their child.
Twenty-seven-year-old Emma Hart's body was found in Henley Close, Tipton, West Midlands on 9 December, 2007.
Her son, Lewis Dangerfield, five, was later found dead in Walker Street, where he lived with his mother.
Black Country Coroner Robin Balmain recorded Ms Hart killed herself and that Lewis was unlawfully killed.
Ms Hart's body was found at her mother's flat.
Just remember, it's all your fault
Note left by Emma Hart
Black Country Coroner Robin Balmain heard Lewis' father, Shaun Dangerfield, had split with Ms Hart and had a new partner.
Mr Dangerfield told the inquest at the Council House in Smethwick that the last text he had received from her in the days before her death had said "I know what to do now for the best" and was signed with a kiss.
He said he thought she meant it was an amicable response to a disagreement they had had over custody arrangements.
The inquest also heard that in notes she had left she told him: "Did you really think I was going to die and allow you to bring up our son... and play happy families?"
She said Mr Dangerfield would now hurt for the rest of his life as he had made hers hell.
Lewis' father, Shaun Dangerfield, said he had lost the largest part of his life
She wrote: "You can enjoy your life now as you have nothing to stop you, ha ha."
She also wrote: "Just remember, it's all your fault."
The inquest heard Ms Hart was found with a cut across her wrist and drugs, including morphine, in her system.
Lewis also had high levels of a painkiller in his system.
It was possible Ms Hart died because of the blood loss from her wrist although the levels of painkiller in her body were high enough to be fatal, the inquest was told.
Mr Balmain said it was "simply spite" that motivated her actions and added it was the most distressing case he had dealt with in 25 years of service.
"I cannot imagine anything so evil as a mother who would be prepared to kill her son to spite Mr Dangerfield," he said.
Referring to a severely critical note she had left for Mr Dangerfield, Mr Balmain said there was nothing to support her words.
"It seems to me he had done everything he possibly could to fulfil his obligations towards his little boy."
After the inquest, in a statement read out by a police officer, Shaun Dangerfield said he had lost the largest part of his life.
"Take five minutes to sit back and appreciate what you have and imagine what it would be like to have all that taken away from you," he said.
Ms Hart's family also attended the inquest and told the coroner she had "idolised" Lewis.
Emma Hart poisoned her five-year-old son Lewis Dangerfield
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