In the past five years the number of illegal immigrants detained or deported from the US has doubled to a record 400,000 per year.

President Obama has promised to reform the system, making it more humane and targeting criminals, but the broad net and rigidly enforced regulations currently in place leave vast swathes of people – including many legal residents – under suspicion and Latino residents are increasingly frustrated by the stalled legislation.

FRONTLINE correspondent Maria Hinojosa delves into the shadowy world of immigrant detention. Her investigation begins in Obama’s home state of Illinois where the Secure Communities programme, designed to target criminals, was initially welcomed on both sides of the political divide. But now officials are losing faith in a system they say has not delivered results and is causing a backlash among immigrant communities. Cases include the family of Roxana Garcia, whose five children – all US citizens – have been without their mother since she was stopped for a minor traffic offence and deported to Mexico after 15 years in the United States.

The year-long investigation has also uncovered evidence of management cover-ups of racism, beatings and even sexual abuse inside immigration detention facilities, where detainees lack the due process and oversight afforded to criminal prisons.