Outside of panto season, it’s difficult to find a dramatist these days who’s keen to write about witches. While the idea of witchcraft might bring a certain primal frisson to some, and a sociological fascination to others, the contemporary theatre has, by and large, stayed away from the subject in recent decades, mainly because of the singular and overwhelming success of The Crucible. Arthur Miller’s classic deployed its political metaphor about the McCarthy period so persuasively that the witch-hunt metaphor created by the play is still regularly used to illustrate the plight of those unjustly persecuted by the authorities.

Rona Munro, though, has no reason to be intimidated. Her track record at recent Fringes, with such pieces as Long Time Dead and Iron, as well as her charming adaptation of Evelyne De la Cheneliere’s Strawberries in January is impeccable. This year she’s taken a very different approach to her story than the study of ideological hysteria audiences have come to expect. Here, the play – in as far as surviving records allow it – is partly a meticulously researched case study of the final witch to be executed in the UK (Janet Horne, in the northern Scottish town of Dornoch in 1727) and partly her imaginative reconstruction of the circumstances surrounding the death of the woman concerned.

These days a well-preserved forty-something, Munro is easy and intelligent company. My question about the level of expectation built up by Miller’s great play is greeted with a warm and endearing smile. ‘What’s interesting about [The Last Witch] is it’s not a Crucible type story of hysteria or even cultural panic which characterised the earlier period of witchcraft in Britain,’ she says.

What’s so intriguing about this event, is not, it seems, the sense of hysteria that surrounded it, but the bureaucratised process that followed, as well as a flaw in this monolithic system. ‘Janet Horne’s execution came 60 years after the witch before her, and the execution was part of a formal legal process,’ Munro explains. ‘There weren’t any other cases because by then lawyers had a lot of trouble dealing with prosecuting someone in those terms – it was after the Enlightenment. But clearly that hadn’t reached Dornoch.

‘The laws had been repealed in England, but they were still on the statute book in Scotland. You couldn’t just shout, “She’s a witch, burn her” – it had to be brought up at the Kirk Session, then it had to go to the Sheriff Court, and after that, because it was a capitol offence, it had to go to the High Court in Edinburgh, then the Privy Council. You weren’t actually allowed under law to accuse someone of being a witch and try them until it had gone that far. What’s interesting about this case is that it didn’t go past the Sheriff Court.’

Munro owes a good deal of her extensive knowledge of the area to a recent fellowship at Edinburgh University, and her findings have led her to some fascinating revelations about Scotland’s witches. ‘You weren’t allowed to torture accused witches in Scotland,’ she says. ‘I was surprised when I started researching it that they didn’t put them through all sorts of things, but they couldn’t. You could deprive them of sleep, but that was about all. And that was about giving them time to contemplate their sins so that they could make a confession. You can see parallels with Guantanamo where they bent that law to the point of leaving people pleading for mercy. The confessions when they came, said so much about the poverty of those communities. It was things like, “The Devil gave me a big cake, and I said OK I’m yours.”’

Munro’s play isn’t a simple historical reconstruction. The playwright has brought a vivacity to the story through adding some spicy motivation to both our witch, Janet Horne, a woman in her 40s with a teenage daughter, and her persecutor, the Sheriff. ‘The Sheriff is a youngish man at a crisis point in his career, who has not had the trajectory of success that he felt he should have had. He’s been a soldier in the 1715 rebellion on the government side, but not particularly distinguished himself. He’s been put in a backwater, and he’s got a lot of chips on his shoulder. There’s also sexual tension, because she’s quite hot, Janet. This is part of what gets her condemned. I think that supernatural element adds to the sexiness, makes it more exciting. We all have a vested interest in preserving the romance of that, but the flipside is you can say, “It wasn’t me, she or he made me do it”.’

Obviously the story can only end tragically, yet there’s a surprising humour that runs through the script, partly arising from the inappropriate sexual chemistry between the two leads. ‘It’s that thing of fancying people you don’t particularly want to fancy, that’s always annoying,’ says Munro. ‘It’s annoying to both sexes, but men had more power to act on it at that time. That said I think she is an incredibly annoying woman generally. I’ve imagined she sees herself as special, which of course makes you want to slap her. But in another way it’s magnificent that you can live in some place like a dunghill at the back end of beyond and see yourself in some sense as a goddess.’

Dominic Hill’s production promises to evoke a lush midsummer rural landscape, with Munro’s characteristically rich but simple poetry part of the appeal. With the remarkably accomplished Kathryn Howden in the lead role, and a strong supporting cast, the piece seems set to create a magic of its own. But does Munro believe in magic? She gives me another bewitching smile, and adds, carefully choosing her words. ‘Well, one of the things about magic is that some of it comes from an evocation of place. If you don’t live in a society that has television and the internet and the cinema, then the scale of nature feels bigger, it becomes overwhelming. I think that’s where the magic really comes from.’

The Last Witch, Traverse Theatre, 228 1404, 23–29 Aug, 7.30pm (27, 29 2.30pm), £10–£25.