No country has more completely outsourced immigration enforcement, with more troubled results, than Australia. Under unusually severe mandatory detention laws, the system has been run by a succession of three publicly traded companies since 1998. All three are now major players in the international business of locking up and transporting unwanted foreigners.

The first, the Florida-based prison company GEO Group, lost its Australia contract in 2003 amid a commission’s findings that detained children were subjected to cruel treatment. An Australian government audit reported that the contract had not delivered “value-for-money.” In the United States, GEO controls 7,000 of 32,000 detention beds.

The second company, G4S, an Anglo-Danish security conglomerate with more than 600,000 employees in 125 countries, was faulted for lethal neglect and abusive use of solitary confinement in Australia. By the middle of the past decade, after refugee children had sewed their lips together during hunger strikes in camps like Woomera and Curtin, and government commissions discovered that Australian citizens and legal residents were being wrongly detained and deported, protests pushed the Liberal Party government to dismantle some aspects of the system.

But after promising to return the work to the public sector, a Labor government awarded a five-year, $370 million contract to Serco in 2009. The value of the contract has since soared beyond $756 million as detention sites quadrupled, to 24, and the number of detainees ballooned to 6,700 from 1,000.

Dangerous Problems

Over the past year, riots, fires and suicidal protests left millions of dollars in damage at Serco-run centers from Christmas Island to Villawood, outside Sydney, and self-harm by detainees rose twelvefold, government documents show. In August, a government inspection report cited dangerous overcrowding, inadequate and ill-trained staff, no crisis planning and no requirement that Serco add employees when population exceeded capacity.

At the detention center Serco runs in Villawood, immigrants spoke of long, open-ended detentions making them crazy. Alwy Fadhel, 33, an Indonesian Christian who said he needed asylum from Islamic persecution, had long black hair coming out in clumps after being held for more than three years, in and out of solitary confinement.

“We talk to ourselves,” Mr. Fadhel said. “We talk to the mirror; we talk to the wall.”

Naomi Leong, a shy 9-year-old, was born in the detention camp. For more than three years, at a cost of about $380,000, she and her mother were held behind its barbed wire. Psychiatrists said Naomi was growing up mute, banging her head against the walls while her mother, Virginia Leong, a Malaysian citizen accused of trying to use a false passport, sank into depression.