Delama Georges lives one stop from the end of the No. 2 train line in Brooklyn, right next to Holy Cross Cemetery. His proximity to so much death did not bother him until Nov. 9, 2011, when he learned that both his parents contracted cholera during a visit to his sister in Haiti. While Georges’ mother lay in a coma, brought on by dehydration from violent vomiting and diarrhea, his father died, joining more than 8,500 Haitians who died in the epidemic, which began four years ago this month.

The tragedy took on a new dimension after a coalition of U.S. and Haitian lawyers from the Boston-based Institute for Justice and Democracy in Haiti (IJDH) filed a class action against the United Nations for the alleged role of Nepalese peacekeepers in contaminating the country’s waterways.

On Thursday, Ellen Blain, an assistant U.S. attorney for the Southern District of New York, will defend the United States’ interest in upholding the international organization’s immunity. Even critics acknowledge that without those protections, the organization would have difficulty recruiting peacekeepers and embarking on missions abroad. The U.S. has said that it has a treaty obligation to protect U.N. immunity in this case and that allowing the case to proceed could harm the country’s relationship with the U.N.

The IJDH will argue that international and national law require the judge to allow the claims, since the U.N. failed to provide victims with an adequate venue for their grievances, as promised in its agreements with Haiti.

The IJDH’s lawyers are demanding three things: funds to fight the ongoing epidemic and clean up Haiti’s rivers, financial compensation for victims and an apology from the United Nations. Implicit in their lawsuit, however, is the far bigger challenge, lawyers say, to the U.N.’s immunity from prosecution.

In 1946, the year of the first U.N. General Assembly, one of the organization’s first acts was to grant itself legal immunity on the basis that such protections are critical to the conduct of international diplomacy. Member states, including the United States and Haiti, are among the signatories to the Convention on the Privileges and Immunities. Since then, the U.N. has never been successfully sued, although attempts have been made.

Mothers of Srebrenica, an association representing survivors of the Bosnian war massacre, tried to sue the U.N. in 2007, alleging that Dutch peacekeepers failed to prevent the killings in 1995 of 8,000 Muslim Bosnian men and boys by Serbian soldiers in a U.N.-designated safe zone. Dutch courts and the European Court of Human Rights rejected that case. In April of this year, however, the Dutch government was found liable in a separate case.

There are, however, official channels for victims of U.N. actions to seek redress. If complaints are made in the context of peacekeeping operations, the host country and the U.N. typically agree to a system for handling these claims. Despite an agreement between the U.N. and Haiti that promised victims the right to file claims for unintentional harms caused by the organization’s personnel, no such system was ever set up. (The U.N. has not offered an explanation, and a U.N. representative declined to comment for this article).

In November 2011, before filing the lawsuit, IJDH lawyers submitted claims through a little-used peacekeeping claims unit in Haiti on behalf of 5,000 Haitians, requesting a minimum of $100,000 for the families or next of kin of each person killed by cholera and at least $50,000 for each victim who suffered illness or injury from cholera. Fifteen months later, the request was rejected.

Patricia O’Brien, the U.N. undersecretary-general for legal affairs, responded in a letter that the claims were “not receivable,” pursuant to the 1946 convention granting the U.N. immunity.

The biggest consequence if the plaintiffs’ requests are met would, for the U.N., be financial. In addition to providing compensation for victims, the lawsuit aims to force the organization to deliver on a $2.27 billion pledge toward an ambitious 10-year cholera-elimination campaign announced in 2012. So far, only 1 percent of that figure has been raised.

In October 2010, the U.N. made a routine deployment of a peacekeeping force to Haiti from Nepal, which at the time was experiencing a surge in cholera infections. The soldiers were stationed on a base near the Meille tributary, which flows into the Artibonite, Haiti’s longest river and primary water source.

Pipes leaking raw sewage, along with improper disposal of water contaminated with human waste, are believed to have contributed to the spread of V. cholerae.

Jonathan Katz, then The Associated Press’ reporter in Haiti, followed up on local rumors about the base that month. “A buried septic tank inside the fence was overflowing, and the stench of excrement wafted in the air,” he wrote.

Scientists soon confirmed journalists’ accounts. The National Public Health Laboratory in Haiti and the U.S. Centers for Disease Control and Prevention published a report in November 2010 showing a link between Haiti’s cholera and strains of the disease active and prevalent in South Asia.

French epidemiologist Dr. Renaud Piarroux went one step further, using doctors’ reports to map cases of the disease according to time and location. These data clusters then helped him narrow the origin of the outbreak to the Haiti’s central plains, in particular, the village of Meille, the site of the U.N. peacekeeping camp. “There was an exact correlation in time and places between the arrival of a Nepalese battalion from an area experiencing a cholera outbreak and the appearance of the first cases in Meille a few days after,” he wrote in a 2011 report.

But the U.N. denies blame. Subsequent reports conducted or commissioned by the U.N. have muddied the waters. Despite the fact that a 2011 independent investigation commissioned by Secretary-General Ban Ki-moon found that the cholera strains in Haiti and Nepal were similar, the report concluded that a “confluence of circumstances,” not the peacekeepers, were responsible for the outbreak.

In response, the IJDH’s complaint accuses the U.N. of having “willfully delayed an investigation into the outbreak and obscured discovery of its source.”

Even critics of the United Nations concede that diplomatic protections for the U.N. are, overall, a “good thing,” said IJDH’s Concannon, allowing the organization to provide alternative justice in countries where local courts do not ensure a fair trial. But he and others say the cholera case shows a U.N. too unwilling to waive its immunity. “The U.N. is currently suffering from an accountability crisis,” said Beatrice Lindstrom, another lawyer working on the case for the IDJH, “one in which they treat ‘immunity’ to mean ‘impunity.’ ”

Brett Schaefer, author of “ConUNdrum: The Limits of the United Nations and the Search for Alternatives,” said the diplomatic-immunity clause is, in some ways, an anachronism. The U.N. of the 1940s was envisioned as a far narrower, largely diplomatic venture. The current scope of the organization, including its peacekeeping missions, allows for much more opportunity for officials to run afoul of national laws, he said.

“They weren’t trying to avoid the prospect of accountability,” said Schaefer. “The U.N. was just an extension of normal diplomatic proceedings between countries.” But today, he said, the organization has applied its diplomatic immunity “too broadly to protect U.N. officials from consequences of negligence, criminality and other crimes.”

José Alvarez, a professor of international law at New York University, wrote in an op-ed that the organization’s handling of the allegations has been “a public-relations as well as public-health disaster.” It is difficult to sympathize with U.N. logic that admits responsibility for small claims, such as traffic incidents, but not larger ones, like those involving the deaths of 8,500 Haitians, he wrote.

“Mr. Ban Ki-moon and the other high officials at the U.N. should hang their heads in shame for not moving more quickly and not being very clear about taking full responsibility,” said Stanley Alpert, an environmental-litigation lawyer involved in the third suit against the U.N. on behalf of Haitian cholera victims.

Alpert’s case, filed six months ago, makes an argument nearly identical to the IJDH’s case, although it tried a more direct approach. On June 20, a summons was placed in Ban’s hands as he stepped out of the Asia Society headquarters on Park Avenue in Manhattan. Bodyguards accompanying him smacked the papers out of his hands and onto the ground, according to Alpert, who was not present. The U.N. maintains that Ban never touched the items.

During a visit to Haiti in July, Ban said the U.N. has a “moral responsibility” to help Haiti eliminate cholera. But the U.N.’s only response to the litigation so far came in March, when the United States filed a response, stating that the U.N. “enjoys absolute immunity.” No U.N. officials are expected to attend Thursday’s hearing.

Whatever the results of that hearing — which could take weeks, or months, to be determined — an appeal is likely. Said Lindstrom, “We’ve always understood the lawsuit to be a tool to keep public attention and pressure on the U.N. to change course and do the right thing.”