Nations at war have always had the legal authority to detain captured enemy soldiers ("prisoners of war") to prevent them from returning to the battlefield. Similarly, the U.S. has the legal authority to detain captured "enemy combatants" in the War on Terror in order to ensure the safety of the nation.
Central to the legality (and morality) of this authority, though, is the determination that the person detained is, in fact, an enemy soldier or combatant. In conventional warfare, this is usually easy, because soldiers wear uniforms. In the War on Terror, however, enemy combatants do not wear uniforms. This is a problem, because it requires us to determine in some fair and reasonable manner whether particular individuals are in fact affiliated with the enemy. It would be unjust and counter-productive for us to detain people who are not actually a threat to us but were innocently swept up in the inevitable chaos of war.
In part for this reason, the Supreme Court has held that individuals detained at Guantanamo have the right to habeas corpus -- that is, they have the right to ask a federal court to determine whether they are being lawfully held. Put simply, the military cannot legally detain an individual at Guantanamo unless it can show by a "preponderance of the evidence" that he is in fact an enemy combatant.
This is, of course, a much more lenient standard than the "beyond a reasonable doubt" requirement we apply in criminal cases, but it is designed to ensure that there is at least a reasonable factual basis for holding an individual indefinitely in a military prison thousands of miles from his home.
In most of these situations, there are no eyewitnesses available to testify to what the accused enemy combatant is thought to have done. Instead, the government's proof usually consists entirely of documents created by members of the military who record what they were told by others. Such documents are frequently prepared in highly stressful situations, based on reports from unknown sources, filtered through interpreters, and subject to transcription errors.
A critical question in these habeas corpus proceedings is therefore whether such documents are sufficiently reliable to meet the preponderance of the evidence standard. The obvious solution is to require the government to present evidence that the documents at issue in any given proceeding are reliable. But a federal appeals court recently held in Latif v. Barack Obama that judges ruling on the legality of these detentions must treat these documents as presumptively reliable. That is, instead of requiring the government to prove that they are reliable, the judge must presume the documents to be trustworthy unless the detainee's lawyer can prove by "clear evidence" that they are in fact unreliable.
This stands any sense of fairness on its head. Indeed, in a powerful dissenting opinion, Judge David Tatel argued that such a presumption of reliability makes no sense when documents are hastily prepared in a highly secretive process in "the fog of war." Judge Tatel is clearly right. The United States has no business holding a possibly innocent individual in indefinite detention in Guantanmo based entirely on information contained in a document that might well be unreliable. As Judge Tatel concluded, the majority's position "comes perilously close to suggesting that whatever the government says must be treated as true."
It is easy to understand the desire to be risk averse about releasing a possibly dangerous individual. But we must also consider the consequences of imprisoning indefinitely an innocent person. Indeed, that concern is supposed to be central to our most basic American values.