A Chinese couple – a nanny and her partner – were due in court in Paris on Tuesday, accused of killing and dismembering the parents of a baby that had died in the babysitter's care.

The crime came to light in June 2012 after two joggers found a naked leg, cut off at the ankle, while running through the Vincennes forest on the edge of the French capital.

Several days later, a guide dog found a human torso in the same area, but the hunt for further remains was fruitless.

Police knew the victims were Asian and initially thought the murders could be the work of the Chinese mafia, or that of Luka Rocco Magnotta, a Canadian convicted of killing and dismembering a Chinese student, who had spent time in Paris.

But before the bodies could even be identified, a Chinese couple – Hui Zhang and her boyfriend Te Lu, both 34 – approached police and admitted to the crime.

Hui told police she had been babysitting a two-month-old baby that had asphyxiated in his sleep.

They decided to offer the parents money to remain quiet about the death.

But when the parents arrived at the home, a furious row broke out, which ended with Hui killing them with a small axe.

Hui claims they acted in self-defence after the parents became enraged and attacked them with a butcher's knife. Her boyfriend had been seriously injured during the struggle.

Trying to cover her tracks, Hui then chopped up the two bodies in her bathroom with an electric saw, using the washing machine to cover the noise.

She then wrapped the parts in rubbish bags and scrubbed her apartment clean.

Following her directions, the police then uncovered more body parts around the forest – although they did not find the baby's body, which Hui said she had thrown in rubbish bins along with some of the other remains.

The baby's grandfather claimed to investigators that the babysitter was giving the child sleeping pills, although other parents praised her service.

Police say there were no previous signs that Hui and Te, who arrived in France in 2004, were pre-disposed to this sort of grisly crime.

Hui has been described by investigators as a highly intelligent and forceful character. Witnesses say she was the dominant partner in her relationship with Te, who was a business advisor.

After the murders, they went to China and closed their bank accounts in France, but returned soon after.

They say they had always intended to return, but police claim they were worried about facing the death penalty in China.