"Thou shalt not suffer a witch to live," advises the King James Bible, and call centre employee Anouska Lacox now stands in the dock for aggravated harassment of her work colleague. Alice Preston has stabbed herself, purportedly owing to a campaign of intimidation let loose on her by Mrs Lacox. In this docu-drama by local playwright Tony Green (who also directs) we are taken through the stages of the process – clerk of the court's introduction, opening statements by prosecution and defence counsels, and then a succession of witnesses tell their tale.

Courtroom dramas have of course been a staple of stage and film for a very long time and number at least two b/w film classics from 1957 alone among their number: Twelve Angry Men (Henry Fonda) and Witness for the Prosecution (Charles Laughton and Marlene Dietrich). Whether the genre makes for effective film drama is a disputed point – naysayers claim that it tends to be a static format, whose stasis has traditionally to be jazzed up with melodrama – witnesses blurting out tearful confessions, revelations of the unfeasibly lurid pasts of blue-rinse matrons – and corkscrew twists of all sorts in the tail. You'd think that just about every variant on the theme had already been done, but Mr Green has come up with the novel – though not, I think, unique – notion of presenting the facts of the case and inviting his audience to determine innocence or guilt by a show of hands. Neither the threat of beheading nor of the electric chair would drag the Thursday night's verdict out of me, however.

There is something almost mediaeval court-like about the ancient complex of abbey buildings housing the Unicorn Theatre, so that the wood-panelled courtroom set with its dock and witness stand gains extra resonance from its architectural milieu. A dash of modernity is stirred into the mix in the form of giant blow-ups of court documents and exhibits, including a pair of offending scissors, a snapshot of the call centre, diary extracts; a simple but clever device. This blend of the ancient and modern is appropriate, too, vis-à-vis the material of our drama since Mr Green's spotlight falls on the vexed, contemporary issue of at what point intercourse between individuals that takes the guise of byplay, needling or teasing amounting to bullying crosses that invisible and disputed line from the just-about-acceptable into the realms of crime.

Under the English adversarial system, defence and prosecution counsels naturally lock horns from the start as they jockey for position alternately with soft soap and bludgeon. As the latter, I thought Maria Crocker struggled a little with the rhythm and emphasis of her sentences, while Adam Blake's defence barrister seemed a touch nervous and his movement was consequently slightly jerky. Both have demanding roles, however, and they demonstrated impressive commitment to them. The procession of witnesses unrolled inexorably by, all plausible in character and manner, and for whom Mr Green has provided appropriately nuanced dialogue: a methodical policeman (John Hawkins, getting us off to a strong start in hitting just the right note of practised, bureaucratic notebookery mingled with a touch of compassion) is succeeded by the call centre manager and the victim's GP. Here Mr Green, backed up by the excellent Duncan Blagrove, sleek in red bow-tie and with mincing walk, gives us a subtle portrait of a professional basking just a little in his own status and superiority, firing out his jargon with relish. These are followed by Lorna Walker's ever-smiling psychology lecturer, full of theory about methods of psychological manipulation. Jon Crowley did that difficult thing of portraying a truly good man – a vehemently and patently sincere healer of body and soul. This was a thoughtful, convincing performance by the actor.

It was clear from the start that the impression made by accuser and accused in the witness box would be paramount in influencing the jury's verdict. In a limited sense the one was an alter ego of the other in that each of them tried to portray herself as an ordinary if hapless citizen in the grip of an upheaval blown in from the blue yonder, and which turned into a gruelling ordeal. Tracy Hughes' edgy if not paranoid complainant was subsequently matched in outburst, though of a quite different sort, by Alex Codling's feisty defendant. Mr Green was particularly well-served by his chosen actors here. Ms Hughes captured just the right blend of her character's vulnerability and stubbornness, while Ms Codling's anger at her predicament and her bewildered proclamations of innocence were wholly persuasive.

This was a densely-written, intelligent drama from Tony Green and Abingdon Drama Club. I was told that its fate will likely be to disappear into the archives, there - one presumes - to gently gather dust. That would be a pity since the production deserves a wider exposure.