The law is an ass, braying to archaic rules that don't always seem to match the punishment to the crime. In America, the government fought back in the war against drugs by tightening federal policy so that anyone found in possession of narcotics could be persuaded to testify against friends in order to reduce their sentence. The logic was that low-level dealers and users would avoid a lengthy spell behind bars by surrendering the names of people higher up the supply chain, allowing authorities to cut off the head of the hydra.

Snitch is an action thriller inspired by real events about a young man, who faces a mandatory prison sentence of 10 years as a result of this aggressive policy, and the father who risks his life to help the police prosecute the men responsible for his boy's predicament.

No doubt, the true story behind Ric Roman Waugh's film is incredible and inspiring - a rousing testament to one man's selfless crusade to save the people he loves. Unfortunately, Waugh's script, co-written by Justin Haythe, fails to tug the heart strings and there's a complete absence of jeopardy. At no point do we fear the father will be injured let alone killed by the ruthless criminal fraternity he intends to single-handedly bring down through brute force and luck.

The hero in question is John Matthews (Dwayne Johnson), manager of a construction firm, who left his first wife Sylvie (Melina Kanakaredes) to begin afresh with Analisa (Nadine Velazquez). Out of the blue, John receives a panicked telephone call from Sylvie: their son Jason Collins (Rafi Gavron) has been arrested in possession of enough pills to earn him a decade behind bars.

US attorney Joanne Keeghan (Susan Sarandon), who hopes to be re-elected on an anti-drugs platform, is sympathetic to John's pleas for leniency but is unmoved. In desperation, John proposes that he will go undercover to bring down a drugs cartel, aided by Agent Cooper (Barry Pepper) and his covert task force. Thanks to an ex-con (Jon Bernthal) on the construction firm's payroll, John makes a connection to local dealer Malik (Michael K Williams), who in turn leads to Juan Carlos Pintera (Benjamin Bratt) aka El Topo. The chance to bring down El Topo is irresistible to Keeghan, who sanctions the undercover operation but makes clear that Jason's freedom depends on bringing down the entire supply chain.

Snitch casts Johnson in his familiar role as a gung-ho hero, who is sketched in broad strokes so we understand John's desire to risk everything, including his happiness with Analisa, for the sake of his boy. Sarandon and Pepper are wasted in two-dimensional roles, but chew scenery when required. Waugh competently orchestrates the action sequences including a confusing finale that descends into an explosive bloodbath.