In 1949 Los Angeles is a city ruled by the mob. At the top of the crime syndicates is Mickey Cohen (Sean Penn), a ruthless mobster involved with murder, women and drugs. To combat Cohen, the police department look to construct a special squad of cops who will shut down his operations. Bill Parker (Nick Nolte) pitches the idea to honest cop John O'Mara (Josh Brolin), who is also a happily married war veteran. His wife gives him the idea of picking men that have little ambition and therefore less likely to be corrupted. One of the main men to join his squad is Sgt. Jerry Wooters (Ryan Gosling), who has eyes for Cohen's etiquette teacher Grace (Emma Stone). The other members of the squad include Coleman (Anthony Mackie), Max (Robert Patrick), Conway (Giovanni Ribisi) and Navidad (Michael Pena), each of whom has their own specialties.

The most depressing realisation about Gangster Squad is not simply that it is the lowest form of pulp trash, but that it leaves in its wake the question of "what if?" Director Ruben Fleischer (Zombieland, 30 Minutes or Less) has assembled a cast that the most seasoned director would salivate over, only to show complete ineptitude towards authenticity and controlled performance registers. The only positive to be drawn from the film is that it contains some momentarily appealing photography. The rest of the film is a shambles. It's badly directed, allowing for poor performances, glossy over-stylisation, and serves no purpose other than showcasing a series of tiresome gunfights.

How did Warners Bros, who produced some of the most important gangster films ever made, let this happen? It's through no fault of the source material. The film is based on a seven day L.A. Times series by journalist Paul Lieberman, who in 2008 chronicled the real life formation of the Gangster Squad. Historical facts notwithstanding, the film is as it claims "inspired by a true story". It's the treatment of the material that fails. Discussing the film's cop-turned-writer Will Beall, Lieberman stated in an article for the Nieman Reports: "With 'The Gangster Squad,' he understood that the studio wanted to go big, with flying bullets and fists." Evidentially, someone at Warner Bros. felt this subgenre had to be modernised by removing the substance and racking up the violence.

The classic gangster films of the past were more psychological than ostentatious. Filmmakers like Howard Hawks used them as public warnings against the real life threat of gangsters and to pressure governments to take stronger action against them. The films provided cautionary tales about the way that ordinary people could be seduced the allure of power and money, raising their social status but dispersing their friends, family and moral values. Actors like James Cagney transformed the gangster figure into tragic Shakespearean characters that were physically and mentally corroded by the failure of the American Dream.

The heavy emphasis on the violence and the action in Gangster Squad lessens the opportunity for complex moral ambiguity. A character asks John late if there is a difference between the criminals and the gangster squad. It's hard to believe given the film's insistence of what a monster Cohen is, along with Penn's disappointingly monotone performance, which substitutes nuances for snarls and angry grimaces. After an opening scene where he orders someone to be drawn and quartered between two cars, there's little by way of sympathy or psychology.

Similarly, if Fleischer is interested in blurring the lines between the criminals and the police, why does he frequently romanticise their battles with adolescent techniques like slow-motion, freeze framing and careless juxtaposition? In one sequence he contrasts a raid with the Carmen Miranda song 'Chica Chica Boom Chic', as the camera crabs sideways, scanning the crew as they beat up crims. Is there any reason besides including a superficial pop reference? This is true of Fleischer's overwrought visual style, one which desperately claws for your attention, only to remain vacuous. There are pretty moments in the film, like a sumptuous wide shot of L.A.'s neon glowing nightlife and Emma Stone's first appearance in a red dress, but they're designed solely to distract you from the film's emptiness and artificiality, as these colour techniques are divorced from a theme.

The performances in this mess range between embarrassing and vapid, and in some cases, both. Brolin's character is a dull lead, the can-do officer with the beautiful home and concerned wife. I found her surprisingly more interesting but the exchanges between the pair gnaw at terrible clichés: "The war is over. Stop fighting," she tells him. When the rest of the cast is allowed to speak, and some of them aren't, they're embarrassed by laughably ornate dialogue, such as: "This is a war for the soul of Los Angeles!" and "The whole town is under water and you're using a bucket when you should be grabbing a bathing suit".

Gosling is the only actor who seems aware of how silly the project is. But his performance is compromised of poses and jokey lines, so chilled that he could play Jerry his sleep. Likewise, Emma Stone's reunion with her Zombieland director leaves her with only two things to do: smoke and look po-faced. The gangster squad itself is little more than a collection of action figurines, defined by quirks than personality, like the knife thrower, the fast shooter and the Hispanic guy.

I liked this movie more when it was called The Untouchables (1987). A tremendous cast and glamorous production design is wasted hosting loosely connected action scenes, with little substance to support them. Warner Bros. decided to delay the film six months following the Aurora shooting. Or was it because they already knew how poor the film was? Now after the events in Connecticut, how will they sell a film that's only interested in gunfire?