“We have nobody going to bat for us, and here comes this woman with her six children and she says, ‘O.K., I’m in your corner and we’re going to fight this,'” said Mr. Bauer, a biochemist injured in a 2002 suicide-bombing in Jerusalem along with his son, Yehonatan, who was then 7. “It did not make Yehonatan walk straighter and it did not make my arm work better, but it did give us hope for justice.”

Ms. Darshan-Leitner, the daughter of a retired dressmaker and teacher who were born in Iran, found her calling while studying law at Bar Ilan University (she also has an M.B.A. from the University of Manchester in England). Fellow students chose her to argue their petition in the Israeli Supreme Court aiming to block the mastermind of the 1985 hijacking of the Achille Lauro cruise ship from entering the country. They lost.

“I understood that I can come on behalf of terror victims, give them a voice, and get my day in a court,” she recalled. “It doesn’t matter what the decision is.”

Her organization, Shurat HaDin, Hebrew for letter of the law, was founded in 2003, and in 2012, the latest year financial reports were available publicly, had 11 employees, three with salaries topping $100,000. It retains not one but two public relations firms, in Israel and New York, pitching Ms. Darshan-Leitner’s perspective on the news. She said the annual budget was $2.5 million, but declined to name her donors, citing security concerns.

The group requires a $600 to $5,000 donation for participants in its mission to Israel, featuring briefings by intelligence agents and observations of military court trials. This summer, it is offering an activist lawyer’s training seminar, with an agenda that includes combating boycotts of Israeli products and defending Israeli soldiers against charges of war crimes.

She claims to have collected $150 million from the various court victories but would not specify which clients got what, citing security again. And she asked that the West Bank settlement where she and her American-born husband, also a lawyer, built a large, immaculate home, not be named, for fear of reprisal.

The successes Shurat HaDin lists on its website, all argued by other firms in American courts, include a $378 million default judgment against North Korea for the 1972 killing of Christian pilgrims at Ben-Gurion International Airport in Tel Aviv by members of the Japanese Red Army; $338 million against Syria for a 1991 kidnapping of archaeologists in Turkey; $156 million against Islamic charities; and $70 million from Iran. The Palestinian Authority, the site says, “quietly” paid at least two confidential settlements. Still pending is a huge case against the Bank of China in which Israel has been fighting to keep Israeli officials having from testifying.