WASHINGTON — The Supreme Court on Monday took away one of the government's tools for prosecuting and deporting workers in this country illegally, ruling that the crime of identity theft was limited to those who knew they were using another person's Social Security number.
People who use false documents can be jailed, the court said. But they cannot be convicted of the more serious crime of "aggravated identity theft" without proof that they knew the identification number belonged to someone else, the court ruled unanimously.
The justices also set the stage for a ruling on long prison terms for juveniles. They voted to decide, in two cases from Florida, whether it was cruel and unusual punishment to impose a life term on a minor as young as 13 for a crime such as rape or murder.
And in an environmental cleanup case from California, the court said corporate polluters should pay for the contamination they caused, not the full cost of the cleanup.
The ruling on identity theft will probably boost the Obama administration's plan to target employers who knowingly hire illegal workers, rather than focusing on illegal workers.
Deportation is usually a slow process if the illegal immigrant does not have a serious felony on his record. But a conviction for aggravated identity theft would most likely lead to a speedy deportation.
Last year, the Bush administration announced roundups of illegal immigrants at several workplaces. Most of those arrested were charged with possessing false documents and aggravated identity theft. For example, 389 workers were detained at a meat-packing plant in Iowa; two-thirds of them were charged with felony identity theft.
The novel use of the law prompted the Supreme Court to take up the issue. Five years ago, Congress strengthened the penalties against thieves who stole identities and used the information to take money from people's bank accounts or charge expenses to them. It called for a mandatory two-year prison term for each offense.
But the court was told that fewer than half of all the possible nine-digit combinations had been used at some time for Social Security numbers.
And the law suggested the criminal had to intend to steal a person's identity. It referred to someone who "knowingly" uses the identification of another person.
The court said the provision did not cover an illegal worker with a phony Social Security card who did not know whether its numbers were those of an actual person.
