The founder of a Haitian death squad who has resided as a free man in New York for most of the last decade is a defendant in a mortgage fraud case that opened yesterday.

The case involving Emmanuel “Toto” Constant has been closely watched by politicians and human rights groups who accuse him of leading a violent campaign against supporters of an exiled Haitian president, Jean-Bertrand Aristide in the early 1990s. Mr. Constant has never served time despite multiple court findings against him regarding actions in Haiti, but his opponents are hopeful that his murderous history could come to light if he is sentenced in this white-collar case.

Mr. Constant waged “a campaign of terror that included gang rapes against women, arson, and killings,” a senior attorney at the Center for Constitutional Rights, Jennifer Green, said in an interview at the courthouse yesterday. “When he came to the United States, he just figured out a different way to exploit people.”

The defendant is the founder of FRAPH, a Haitian paramilitary group that tortured and killed thousands of Mr. Aristide’s supporters after he was overthrown in a coup. Mr. Constant fled to America after American troops helped restore Mr. Aristide to power, and the American government declined to deport him to stand trial in Haiti. Critics say that decision stemmed from his role there as a paid informer for the CIA — a seemingly paradoxical relationship, as his group opposed America’s intervention.

Mr. Constant lived in New York for the next 10 years, until he was arrested for mortgage fraud in 2006. He reached a plea agreement with the government that would lead to his deportation to Haiti without serving further jail time on the fraud charges. Then, a judge rejected the plea agreement after hearing testimony from advocates who claimed that the defendant might not be properly punished for his human rights violations under Haiti’s tattered legal system.

“Given who he is, he should not have gotten a slap on the wrist for economic crimes,” Ms. Green, who participated in the effort to try Mr. Constant in New York, said. The Center for Constitutional Rights has organized several rallies outside the courthouse in the last month.

Ms. Green said she is hoping that the defendant’s record will earn him several decades in prison, the toughest possible sentence in his mortgage fraud case. Haitian courts have convicted Mr. Constant in absentia for his involvement in massacres there, and in 2006 an American court ordered him to pay $19 million to three women who were gang-raped by his soldiers.

Mr. Constant’s attorney, Samuel Karliner, noted that many of the conspirators in the defendant’s alleged fraud ring received light sentences for cooperating with the government. The fact that Mr. Constant’s plea deal was thrown out is “outrageous,” he said.

“They seem to believe that our government should punish him for his crimes in Haiti,” Mr. Karliner said, referring to the human rights advocates monitoring the case. “He should be punished appropriately in this case if he is found guilty. To punish him for an allegation in Haiti is wrong.”

Mr. Constant has been charged with defrauding lenders in New York while working as a real estate broker. He and his co-conspirators allegedly pocketed cash by lying about property values in mortgage applications.

“Some people, like Mr. Constant, figured out how to pull the wool over the banks’ eyes,” the prosecutor, Tom Schellhammer, said in his opening statement yesterday.

Mr. Karliner responded that his client was not a knowing participant in the mortgage scheme. Neither side referred to Mr. Constant’s activities in Haiti during their arguments.

The defendant has already served close to a year of a sentence stemming from a similar fraud ring on Long Island.