A New York mother has been sentenced to 20 years in prison for murdering her son with a salt overdose, which she did to attract social media attention over his illness.

Lacey Spears, 27, detailed her five-year-old son’s illness on a blog called “Garnett’s Journey” and other social media outlets, Reuters reports.

The jury, in Westchester, convicted Spears of second-degree murder, finding that she put a lethal amount of salt into the boy’s feeding tubes in hospital, while updating her blog and social media accounts with news of his illness.

Doreen Lloyd, Assistant District Attorney, told the court that the five-year-old Garnett was a healthy child and whose illness was entirely the result of his mother’s actions.

“She continued to portray him as a sick child for her own bizarre need for attention. She used that feeding tube as a weapon to kill him,” Ms Lloyd said.

“Garnett Spears should be in school today but he's not because his mother murdered him,” she said.

“Throughout his five years, Garnett Spears was forced to suffer through repeated hospitalizations, unneeded surgical procedures and ultimately poisoning with salt, all at the hands of the one person who should have been his ultimate protector: his mother,” Westchester District Attorney spokeswoman Janet Di Fiore said following the conviction.

The defence claimed Spears was innocent and attributed the boy’s death to hospital negligence.

Spears had told prosecutors that the boy suffered from a range of serious illnesses, including ear abnormalities and Crohn’s disease, Newsweek reports.

The child had been hospitalised with gastrointestinal symptoms, which the prosecution said his mother had induced.

Spears posted about the child’s condition regularly, even posting photos of his final few hours on life support.