"It was devastating," recalls the soft-spoken Palestinian immigrant, who months later learned that he was being held on hearsay allegations - many furnished by his bitter ex-wife - that he belonged to a terrorist group and had plotted to bomb the World Trade Center.
Mr. Kiareldeen is now free, after seven judges reviewed his case and flatly rejected government claims that he posed a threat to national security. Still, he has never seen the classified report used to jail him.
Alarmed by a growing number of cases such as Kiareldeen's, Congress and the courts are increasingly questioning the constitutionality of the little-known laws, which have been used in efforts to deport dozens of immigrants.
The debate over secret evidence underscores a historic tension in America between the goals of individual liberty and national security.
It also highlights the widely divergent legal treatment of immigrants and US citizens. Critics, including lawmakers and civil rights groups, decry the use of concealed evidence as unfair, Kafkaesque, and a throwback to the McCarthy-era purges of alleged communists.
"Essentially the same tactics directed at communists in the 1950s are being directed against alleged terrorists in 2000," says David Cole, a Georgetown University law professor. Since 1987, Mr. Cole has represented 13 immigrants against whom the government has sought to use secret evidence.
The laws have existed since the 1950s, but were expanded and strengthened in 1996 in a wave of antiterrorism legislation following the Oklahoma City bombing.
On Capitol Hill last week, the House Judiciary Committee held hearings on a bipartisan bill, co-sponsored by 90 lawmakers, that would end the use of secret evidence in immigration deportation hearings.
Backers of the bill range from conservative Republican Bob Barr of Georgia to House minority whip David Bonior of Michigan, a liberal Democrat.
Meanwhile last Wednesday, following a pattern of recent court decisions, a federal district judge in Miami ruled that the government's use of classified evidence had "violated" the due process rights of another Palestinian immigrant. The judge ordered a new bond hearing for Mazen Al-Najjar, a former professor and father of three who has been held since 1997.
Federal agencies charged with combating terrorism say that the use of secret evidence is limited, but vital. "We take these matters seriously, and we do not casually resort to the use of classified information," Bo Cooper, general counsel for the Immigration and Naturalization Service, told the House Judiciary Committee last week.
Out of nearly 300,000 immigration cases reviewed and prosecuted by the INS each year, only 11 cases now pending involve secret evidence, he said. About 50 cases were filed between 1992 and 1998, lawmakers say, the majority involving Arab or Islamic immigrants.
FBI and INS officials warn that repealing the laws would allow terrorists to escape deportation. Indeed, it would "[extend] the privilege of United States citizenship to those who are undeserving because they are dangers to the national security," Mr. Cooper stressed.
Under current law, any classified evidence deemed "relevant" can be used both to deny immigrants entry at the border and, once they are here, to oppose their applications to avoid deportation. The evidence need not show that the immigrant poses a national security risk. Moreover, since at least the 1960s, the INS has used such evidence to lock up immigrants as long as deportation hearings are under way.
At the heart of the argument for secret evidence is the idea that immigrants do not enjoy the same constitutional rights that citizens do, and therefore the government does not have to reveal sensitive information being used against them.
We don't have to release as much information [in immigration cases] as we would have to in a criminal case," where the standard of proof is much higher, says a senior INS official who requested anonymity.
But critics say such sweeping use of secrets to detain and deport immigrants is a violation of the Fifth Amendment, which holds that "no person" - not "no citizen" - shall be denied liberty without the due process of law. No confidential evidence is allowed in US criminal trials, including those of terrorists and spies, they note.
"The most basic protection of the due process clause is the right to know the charges and to defend oneself, but the use of secret evidence eviscerates that right," says Cole.
A string of judicial decisions has tended to support the view of Cole and other critics that the use of classified evidence in the name of national security is unfair and can cover up shoddy and unwarranted government prosecutions that rely heavily on "hearsay" in the form of reports by FBI agents.