It doesn’t happen very often, but occasionally a documentary comes along that makes you question everything, puts a new slant on life and death, the whole shebang.

Or just gives you a damn good scare. Paul Hamann’s ‘Fourteen Days In May’ definitely fits the bill.

Shot over two weeks during the summer of 1987 at the infamous Mississippi State Penitentiary – AKA Parchman Farm – ‘Fourteen Days In May’ follows a young black man Edward Johnson as he prepares for – and, with the help of his lawyer Clive Stafford Smith, tries to evade – the gas chamber.

First shown on the BBC over 30 years ago, it has become a landmark film. Similar areas have recently been explored by Werner Herzog, Louis Theroux and Nick Broomfield, but arguably ‘Fourteen Days In May’ trumps all of them for sheer emotional impact.

It explores the inner workings of a prison geared up for taking human life. Astonishing shots shed light on a kind of modern slavery, with policemen on horseback brandishing shotguns, calling out loud reprimands and instructions to large groups of (almost exclusively) young black detainees as they dig ditches or clear roadside vegetation.

Elsewhere we are witness to the last few minutes of another (white) inmate’s life as he is strapped into the electric chair, though thankfully we don’t see the moment of truth. The gallows humour of both the killers and killed will linger long in the memory.

As ‘Fourteen Days In May’ moves painfully and inexorably on, it becomes increasingly clear that Johnson is innocent. But no-one can do anything about it. Various (black and white) prison officers bravely profess their doubts as to his guilt, while Johnson’s family rally around the quiet, unfailingly polite young man, singing him songs to keep his spirits up.

Hamann breaks the fourth wall to says his goodbyes to Johnson in a memorable scene. But shorn of a voiceover or title cards, ‘Fourteen Days In May’ offers no explicit critique of capital punishment. It doesn’t need to. The facts do that for themselves.

It would seem churlish and pointless not to reveal the ‘ending’ of the film here – Edward Johnson meets his maker. The crushing coda reveals that a young black woman came forward after the execution to verify that she saw him in a pool hall during the time of the alleged crime, but when reporting this to a white police officer soon after was threateningly advised to mind her own business.

What do we take away from ‘Fourteen Days In May’? The only correct response would seem to be rage. And fear. But after that, there’s a helplessness and a slow-burning disgust.

The only slight light at the end of the tunnel is the knowledge that it was in direct response to this documentary that the Lifelines organisation was set up, arranging pen pals for death row prisoners. Stafford Smith has also founded Reprieve.

Is America still like this? The suspicion would have to be that it is.