A 7-year-old's tearful testimony sent his mother to prison for killing his sister in a wading pool.

Amanda Lewis is currently serving a lifetime prison sentence for drowning her little girl in a paddling pool eight years ago.

Her 7-year-old son, AJ, said he saw the whole thing and it was his testimony which got his mother convicted.

Footage from the trial shows him telling a courtroom of people he saw his mother hold his half-sister Adrianna face down in the water.

The prosecutor asks him to explain the meaning behind a drawing showing stick figure standing around a pool.

“That’s my momma,” he says. “Killing my sister.”

Asked how she was doing it, he replied, “Putting her hand over her face.”

The picture AJ drew in court. Source: ITV

The clip appears in the second episode of Piers Morgan's new documentary series Killer Women, which focusses on Lewis' crime.

Lewis, who was a 27-year-old single mother at the time, has consistently denied being responsible for her daughter death.

A denial she re-iterated when Morgan asked her outright if she'd done it.

Amanda Lewis on Killer Women. Source: ITV

Lewis maintains Adrianna had been cleaning bugs out of the water when she slipped and drowned in the water, she called an ambulance but it was too late.

Despite her claims, which were verified by a polygraph test, AJ told his grandparents, and later police and child experts, he'd seen his mother push her over and hold her down.

"She done some stuff that she ain't suppose so my mama got mad, so she throwed her in the pool," he told police.

The trial footage shows him bursting into tears after failing to recognise his mother in court.

After the episode aired viewers took to social media to debate Lewis' innocence.

Many expressed their heartbreak for the child and asked the obvious question: what possible reason could a 7-year-old have to lie?

Feature image: ITV