Was Kayla Mueller's situation different from other Islamic State hostages?

Mueller was the last U.S. hostage known to be held by the militants; now just one British hostage remains.

Three other Americans held by the group, journalists James Foley and Steven Sotloff and aid worker Peter Kassig, were beheaded by the Islamic State in horrific videos that were deliberately spread over social media last year. That same fate also met a number of other foreign nationals, including two British hostages and two Japanese hostages. Some hostages of other nationalities have been released after ransoms were paid; both the United States and Britain publicly refuse to pay ransoms.

Among those who knew of Mueller's capture -- which her family had asked not to be made public -- there was speculation about whether she faced the same threat. As the last known American hostage, was she uniquely valuable to her captors? Would the Islamic State kill a female hostage as brutally as they did a male? Or would she be treated differently?

In general, women are certainly treated very differently from men in the Islamic State. A United Nations report published last year portrayed severe restrictions on women living in Islamic State-controlled territory: Women have "largely been confined to their houses, excised from public life," the report noted, adding that all females over the age of 10 were required to wear veils and that unmarried women could be forced to marry militants.

The Islamic State itself has emphasized the positives of such an extreme patriarchy. In documents attributed to the Islamic State, women are portrayed as mothers and homemakers in the group's new society, and men are bound to protect them. Of course, these documents are at least partly propaganda: There's no doubt that plenty of women have suffered incredible violence at the hands of the Islamic State, from the Yazidi women treated horrendously as slaves to various reports of individual women being executed.

According to the Arizona Republic, the Islamic State made a number of specific threats to kill Mueller in 2014, but never carried them out. The Islamic State rarely used violence against women for propaganda purposes, however, and may have been aware that such violence would prove unpopular. A widespread backlash from Arab Muslims to the group's killing of the Jordanian pilot, Lt. Muath al-Kaseasbeh, could have made the group more cautious about public acts of violence.

Despite this, a number of experts hesitated to say whether the Islamic State would have publicly killed a female prisoner, arguing that the group has certainly proven unpredictable in the past. "They have not played by any set of norms or rules that would inhibit or limit their savagery," Mia Bloom, a professor of security studies at the University of Massachusetts, explained in an e-mail.

The group has looked to theological and historical justifications for the use of extreme violence in the past. However, the escalation of this violence has required new justifications. After the video of Kaseasbeh being burned to death was released last month, some pointed out that immolation was prohibited by the Islamic faith. To respond to this, clerics from the Islamic State issued a fatwa justifying death by fire when used for retribution, pointing to obscure historical and religious precedents that most Islamic scholars disregard.

"The way ISIS justified the immolation of the pilot is the way it justifies many of its brutal acts," Hassan Hassan, an analyst with the Abu Dhabi research center Delma Institute, explained using an acronym to refer to the Islamic State. "It relies on genuine but isolated incidents in Islamic history." The group might have tried to do this again, but theological justification for killing a female prisoner is certainly not obvious: Will McCants, Director of the Brookings Institution's Project on U.S. Relations with the Islamic World, said he can't think of any instances in the Quran that indicate the prophet Muhammad did anything similar.

Regardless of theological arguments, it's possible that a greater motivation -- a desire to shock and horrify -- may have led the Islamic State to take more drastic action. "It is pretty clear that ISIS is working an escalating strategy on its media releases," J.M. Berger, an analyst who follows jihadist movements online, says, pointing to the Kaseasbeh video. "I think ISIS would not balk at killing a woman hostage on camera as part of that process, but they would hold that card until they needed it."

Berger also points out that if "maximum media impact" was what was desired, there were other ways to get it. "For instance, they could have tried to coerce [Mueller] to marry one of their fighters," he added.

Speculation about that possibility grew on Tuesday evening when an unnamed counterterrorism official told ABC News "ISIS didn't see her as a hostage or a bargaining chip."

So far, we only have the Islamic State's account of Mueller's death. Given the group's history of deception, some argue that this account cannot be trusted. Last week, Mohammad al-Momani, Jordan's media affairs minister, called claims Mueller was killed by a bomb from his country's air force "part of [the Islamic State's] media spinning/PR campaign, and it's not the first time they do this." Just recently, there has been speculation that the Islamic State had digitally altered some of the video showing its killings, and Jordan says that Kaseasbeh was killed a month before the Islamic State announced it. Some outside analysis of the Islamic State's statement on the death of Mueller have pointed out inconsistencies.