Ghanaians are waiting for their normally slow court system to deliver a verdict in a shocking case that illuminates resurgent beliefs in witchcraft.

Six people are currently appearing before a magistrate at Tema, near Accra, for allegedly burning a 72-year-old woman to death, in the belief that she was a witch. Earlier, the media had made fun of an elderly woman who, it was claimed, was "arrested" by villagers who claimed that she had "fallen out of the sky" after running out of "witches' gas" on a flying expedition with her coven, and fallen under a tree.

In both cases, anyone with the slightest knowledge of dementia would recognise symptoms of the disease from the accounts given of the behaviour of the women. They were where they were not supposed to be, and when they were asked what they were doing there, they could not explain themselves. This is because dementia sometimes robs its victims of the ability to speak coherently.

The woman who was burnt to death, Madam Ama Ahima, hailed from Ajumako Assasan in the Central Region. She was found in a bedroom of a house in which she knew no one. She had alighted from a lorry at the wrong place and got lost. But she could not explain this and a mob soon gathered around her and subjected her to angry questioning. One of the questioners happened to be an "evangelist", and the suggestion soon gained ground that she was a witch.

A member of the mob asked for kerosene and matches, poured the kerosene on the woman and set her ablaze. A nurse who lived next door heard of the commotion and took the victim to a police station, where she lodged a complaint. The police rushed her to a hospital but within 24 hours, she was dead.

Because belief in witchcraft forms part of Ghanaian mythology, elderly women are often subjected to cruel treatment and mental torture. A lack of scientific knowledge of the natural physical and mental degenerations that can occur during old age – including Alzheimer's disease, but not excluding hysterical dissociation and schizophrenia – means that witchcraft is blamed for a lot of "strange" happenings.

At the same time, a lot of Ghanaians have studied the Bible in a patchy sort of way, and swallow in a literal manner stories about the "casting out of devils". An evangelist who wants to be feared as one who casts out devils cannot lose if he or she picks on an elderly lady. Such women are vulnerable, and where the congregation is itself predisposed towards believing she is a witch, she has no chance. Cruel, brutal acts of "exorcism" are often used to "cure" her.

Many of the latter-day evangelists are ruthless religious mercenaries, who implant the idea in people's minds that nothing bad can happen to them without malign intervention by witches in their families.

So, a marriage breaks down, due to infidelity or pecuniary hardship, and the older woman in the household is responsible. A young, unemployed man becomes listless and shows signs of depression: an elderly lady wants to destroy him. A lorry driver gets drunk and crashes his vehicle at night: an elderly woman shone a torch into his eyes and blinded him, running his vehicle into a ditch. Even simple things such as pupils failing exams, or crops failing, or an inability to save money, are laid at the doors of "witches".

Swaths of Ghanaian society absolve themselves of personal responsibility in almost all things, and, with the aid of both traditional superstitions and the modern equivalent preached in the "charismatic churches", embark on acts of brutality against helpless scapegoats, such as occurred at Tema.

As many as three "witches' camps" have been established in the northern region of Ghana – the Gambaga camp in the East Mamprusi district, Tindanzie camp in the Gushegu district and the Tindang camp in the Yendi district – where elderly women alleged to be witches have been dumped by members of their families. They would probably have lost their lives had they not been placed in the care of government officials and non-governmental organisations. A 55-minute film, called The Witches of Gambaga, co-produced and directed by a Ghanaian-British filmmaker, Yaba Badoe, tells the story of one of the camps. It won the 2010 Black International Film Festival best documentary award.