South Africa’s leading pro-euthanasia activist Sean Davison is facing a second charge of murder.

The 57-year-old New Zealand-born forensic scientist is the founder of right-to-die organisation DignitySA.

He was arrested in September this year in connection with the death in 2013 of his friend Anrich Burger, who had become a quadriplegic after a car accident.

Prosecutor Megan Blows said in Cape Town’s Magistrate Court on Friday morning: “We are in a position to add another charge of murder. Needless to say, the charges are provisional and may change.”

He is accused of intentionally killing Justin Varian in 2015 by placing a bag over his head and administering helium.

Mr Varian had been diagnosed with motor neurone disease some years before.

Mr Davison became a campaigner for the right to assisted dying after he was arrested in New Zealand in 2010 for helping his 85-year-old mother, who was ill with terminal cancer, to die four years earlier.

Archbishop Desmond Tutu gave him a character reference and wrote to the judge calling for leniency.

In the late 1990s, he had helped South Africa's Truth and Reconciliation Commission, chaired by Archbishop Tutu, to identify the remains of anti-apartheid activists.

The forensic scientist served five months of house arrest in New Zealand after pleading guilty to assisted suicide, before returning home to his family in South Africa.

During his last court appearance in September, his lawyer maintained he had not committed any offence.

He is currently on bail, and the case has been postponed until 29 January to allow for further investigations.