Courtrooms, like theatres, draw on claustrophobia to compel. The closed-door atmosphere, sealed off from the quotidian, lends contrived outcomes the inevitability of fate. If Iphigenia in Forest Hills offered no more than courtroom drama, Janet Malcolm’s instinct for story would still enthral. But it’s her instinct for literature that electrifies here.

In lucid, rhythmic sentences, Malcolm recounts the 2009 trial of Mazoltuv Borukhova and the man she was convicted of hiring to kill her ex-husband. The murder was spectacular in the strict sense: Daniel Malakov was shot in a playground in front of his four-year-old daughter. Michelle Malakov, the daughter, was the subject of a custody dispute, adduced as the motive for the murder.

“We take sides as we take breaths,” writes Malcolm. She acknowledges her sympathy for Borukhova, an Orthodox Jewish immigrant from Central Asia. Black-clad, with her long, dark hair bound in red, Borukhova looks “like a nineteenth-century woman-student revolutionary” – or a character conjured by Dostoevsky. And, as in the best novels, Borukhova is a complex figure. She can be mulish, grasping, aloof, “setting off serious allergic reactions”. Did she do it? The evidence is inconclusive, and the question secondary. What scandalises Malcolm is how unjustly the law dealt with this case.

The fiction of judicial impartiality is relentlessly unpicked. Borukhova’s judge has “the faux-genial manner American petty tyrants cultivate” and his hostility to her is egregious. Concerned about his upcoming holiday, he even rushes the final summations. Borukhova’s attorney is obliged to prepare his crucial speech overnight and turns in a sleep-deprived performance. Malcolm’s observation that trials are about “competing narratives” is chillingly endorsed when the jury finds against his client.

Though Borukhova had accused Malakov of molesting their daughter, a few weeks prior to the murder a family court had ordered her to hand over custody to him. Whatever the truth of her allegation – it’s one of the uncertainties of the affair – the decision to remove a happy child from her mother was astonishing. Malcolm detects the influence of David Schnall, Michelle’s court-appointed guardian, who detested Borukhova. When Malcolm talks to Schnall, his malevolence is so striking that she abandons journalistic convention and faxes her notes to Borukhova’s attorney – fruitlessly, as it happens.

Another extraordinary moment comes when Malcolm sees Michelle pedalling her tricycle vigorously along the street while laughing in a “forced and exaggerated manner”. There’s something shockingly disturbing about this small apparition. Previously, Malcolm has remarked that in life things are not always “this or that, but can be both”. Constrained to deal in innocence and guilt, courtroom discourse is always artificial. Literature, by contrast, complicates: it’s so entwined with not this or that, but both that ambiguity might be its precondition. Borukhova is flawed, possibly to the point of committing murder, but has also been appallingly treated. As for Michelle, she is the Iphigenia of the story: the innocent sacrificed to adult schemes. Her terrible laughter, which can neither be accounted for nor forgotten, reminds us that, unlike her mythic counterpart, she has yet to be avenged.