Guantanamo Bay detainees have lost a series of court battles over the past 18 months as appellate judges in Washington have repeatedly sided with government lawyers and against suspected militants seeking to win their freedom.

The U.S. Court of Appeals has not affirmed a single decision ordering the release of a detainee, nor has it reversed any decision that favored government lawyers. The Justice Department even won a case in June in which it had little expectation of victory.

A 2008 Supreme Court decision allowing those held at Guantanamo Bay, Cuba, to challenge their detention was followed by an initial round of district court rulings that ordered the release of dozens of terrorism suspects after the government’s evidence was found wanting.

But the more recent appeals court decisions, which have drawn little attention, have scuttled that trend as circuit judges have displayed more skepticism about detainees’ stories. That has meant an easing of pressure on the Obama administration to resettle or repatriate the men.

“I doubt any of my colleagues will vote to grant a petition if he or she believes that it is somewhat likely that the petitioner is an al-Qaeda adherent or an active supporter,” Judge Laurence H. Silberman of the U.S. Court of Appeals for the D.C. Circuit wrote in April.

The appeals court has not only reversed judgments against the government but has also compelled the lower courts to assess evidence in a manner that is much more sympathetic to government arguments. In one ruling, the appellate judges said the lower courts should consider that “two unreliable pieces of information may corroborate each other.”

“The D.C. Circuit is much more deferential to the government than the district courts are, on average,” said Benjamin Wittes, a senior fellow at the Brookings Institution who has written extensively on detention issues. “And there is a tolerance for the idea that these judgments may end up being imperfect.”

A lower bar

These cases often turn on whether prosecutors can prove that a “preponderance of evidence” shows that a detainee was “a part of or substantially supported” al-Qaeda or the Taliban, and was in the armed forces of one of those groups when captured.

That burden of proof is significantly lower than what is required in criminal courts, where evidence must be “beyond a reasonable doubt.” But even so, prosecutors in the detainee cases often failed the “preponderance of evidence” standard, according to U.S. district court judges in Washington, where 38 detainees won their cases.

Many more cases from among the 170 detainees remaining at the Guantanamo Bay military prison are in the pipeline, but now the government is winning.

In one case, Hussain Salem Mohammed Almerfedi, a Yemeni who was arrested in Iran and turned over to Afghan authorities and then to the United States, argued that he was an economic refugee who was attempting to get to Western Europe when he was picked up by the Iranians in late 2001.

In July 2010, U.S. District Court Judge Paul L. Friedman ruled that the evidence against Almerfedi was too weak to justify his continued detention.

Within the government, there was some debate about whether it was worth appealing the decision. An interagency task force had cleared Almerfedi for repatriation to Yemen or transfer to another country. And some officials concurred with the ruling.

“The case was very, very weak,” said one administration official, who would discuss the internal deliberations only on the condition of anonymity.

The government nonetheless took the case to the U.S. Court of Appeals. Its request was limited — prosecutors sought to have the case sent back to the district court for re-argument — but the appeals court went further, reversing the district court’s decision. The appellate court ruled in June that the writ of habeas corpus, the centuries-old legal doctrine that allows prisoners to challenge their confinements in court, should be denied to Almerfedi.

“The Department believes that the detentions upheld by the court of appeals are all well supported by the facts of the particular cases and are consistent with the rule of law,” Dean Boyd, a Justice Department spokesman, said in a statement.

The Supreme Court’s say

The Supreme Court’s 2008 ruling, in Boumediene v. Bush, extended the right of habeas corpus to Guantanamo Bay detainees and gave wide latitude to lower courts in determining how to handle the cases.

District court judges soon began to rule against the government with some frequency, but as early as February 2009, a three-judge panel decided that federal district judges do not have the authority to order the release of a detainee into the United States. Several subsequent decisions have strengthened the government’s ability to detain.

In January 2010, in its first review of a detainee case, the D.C. Circuit rejected the idea that international laws of war — which limit whom governments can confine during conflicts — apply to the detainees at Guantanamo Bay. That cleared the way for the government to hold captives if they were “part of” or supported al-Qaeda or the Taliban, regardless of the extent of their involvement in a conflict.

The detainee in that case — Ghaleb Nassar al-Bihani, a Yemeni who traveled to Afghanistan in response to a religious call by a Saudi cleric in 2001 — admitted to being a cook for the 55th Arab Brigade, a group of al-Qaeda fighters, and staying at al-Qaeda guesthouses.

“This decision means that al-Bihani could be detained as ‘part of’ al-Qaeda without any regard for what he did for al-Qaeda,” said Stephen I. Vladeck, a law professor at American University who was part of a legal team that challenged the Bush administration’s use of military commissions at Guantanamo Bay. “Whether or not you held a gun or participated in plotting a particular attack, the D.C. Circuit has decided that when you prove membership, it’s divorced from substance.”

Stories meet skepticism

That has made the appeals court much less likely to accept the explanations of detainees who say they were in Afghanistan for charitable work or purposes other than fighting.

In one case, Judge Brett M. Kavanaugh, reversing a lower-court ruling granting habeas, said the account of Uthman Abdul Rahim Mohammed Uthman, a Yemeni captured at the Afghan-Pakistani border near Tora Bora on Dec. 15, 2001, “piles coincidence upon coincidence upon coincidence.”

“Here, as with the liable or guilty party in any civil or criminal case, it remains possible that Uthman was innocently going about his business and just happened to show up in a variety of extraordinary places — a kind of Forrest Gump in the war against al-Qaeda,” Kavanaugh wrote.

Legal experts said it is no surprise that the appeals court is aggressively using its discretion to fill in gaps left by the Supreme Court. The D.C. Circuit has five conservative judges, and some of them have been outspoken in their criticism of the Supreme Court’s decision to extend habeas to detainees. Judge A. Raymond Randolph, speaking at the Heritage Foundation, described the habeas litigation as a “legal mess.”

Shane Kadidal, a lawyer for the Center for Constitutional Rights, a group that represents five detainees and assists other lawyers in dozens of habeas challenges, said: “It is obvious that the judges are trying to take some of the teeth out of the Boumediene decision. . . . For some of them, it’s ideological. They believe that Boumediene was wrongly decided, and this is exactly the approach you would take if you felt this way.”

But moderate and liberal judges on the appeals court have joined in some of those decisions. In the Almerfedi case, for instance, Judge Judith Rogers, a Clinton appointee, joined the reversal.

John O’Quinn, a former senior Justice Department official in the Bush administration, said the lack of dissent among appellate judges makes it harder for detainees’ lawyers to get the Supreme Court to take their cases. Indeed, the high court has rejected all efforts to revisit the habeas litigation.

For defense lawyers, there is a mounting sense of futility. The D.C. Circuit “appears to be dead set against allowing detainees to prevail,” said David Remes, one of Almerfedi’s lawyers. “But as long as we have any arguments available to us, we have a duty to our clients to press them. We have to fight. This is the avenue our system provides us. And it’s the only system we have.”

Staff researcher Julie Tate contributed to this report.