Australian cop flick Felony opens with a perfunctory action scene – the only scene in the film that fits that description. Detective Malcolm Toohey (Joel Edgerton, star and screenwriter) gives chase to a crim fleeing the scene, and earns a deposit of lead in his bulletproof vest for his trouble. Struggling to his feet, he thanks the perpetrator – now restrained by his colleagues – with a roundhouse punch to the face.

His actions are understandable, and hardly a disproportionate response. They’re also – undeniably – illegal, an example of casual police brutality. This kind of shit goes down all the time, no doubt. “If we cop it, they cop it.” But it’s also evidence of the systematic low-key corruption that tends to invade any enforcement agency, where things gradually creep towards good guys are the bad guys. It’s the kind of behaviour that leads to situations like that of Palm Island in 2004, or Ferguson in 2014. It’s the kind of attitude that lets a sloshed cop – Edgerton again – slip past an RBT, grievously injure a young boy and have his misdeed covered up without question.

Felony filters the thin blue line through a prism of such minor corruption, refracted into the form of Edgerton’s morally conflicted detective, the veteran more than happy to conceal his role in the young boy’s injury (Tom Wilkinson) and Wilkinson’s partner, a young, upstanding recruit (Jai Courtney) with more than a few questions about his superior officer’s behaviour. The concept is compelling and the opening half hour is promising, but unfortunately the film’s underwhelming approach reminds us why most big screen police corruption is on a slightly bigger scale.

Part of the problem is that Felony doesn’t have a great deal new to say after its initial half hour. The central moral conflict – does Edgerton confess, and leave his wife (Melissa George) and two sons without a father, or does he carry his punishment “up here” (as Wilkinson urges, pointing to his temple)? The “right” answer is pretty obvious, and unfortunately neither Edgerton’s screenplay nor Matthew Saville’s direction do much to complicate matters.

The characters are broadly drawn from cliché and never transcend that, with little emphasis placed on any character elements not directly related to police work. Melissa George is given astoundingly little to do as Edgerton’s wife: tellingly, when he confesses his crime to her, she remains out of focus in the background so we’re denied even the emotions of her reaction. Wilkinson is a casually racist recovering alcoholic; Courtney is strait-laced but naïve. We’ve seen it all before. The film hints at developing subplots that would give more meat to the film – for example, an investigation into a suspected paedophile – but they don’t go anywhere substantial.

The aesthetic approach to the material doesn’t help matters. Felony is filmed with a steely slickness – sombre blues and metallic greys in the halo of bright fluorescent lights – that’s antithetical to the material. This kind of personal, moral drama calls for a more realist approach, not a sub-Fincher look. It’s not that it looks bad – and there are some effective shots here, as when a garage door rumbles down to envelop Edgerton in darkness – it’s simply ill-suited to the subject matter.

I suspect there was a good film to be made here, a film that more broadly reveals and examines the allure and effect of small-scale police corruption – an Australian equivalent of Child’s Pose. Unfortunately Felony is too simplistic and conventional to fulfil that potential.