A few years ago, Mohammad Abu Ta'a discovered that some storage trailers had disappeared from a plot of land in Jerusalem belonging to his family. Then, the family received a letter informing them they were now trespassers.

When the Palestinian landowner contacted Israeli land authorities, he was told the government had expropriated the land and handed it over to a leading organization that oversees Jewish settlement building in the West Bank. That group, Amana, is now building its new headquarters on the land.

Abu Ta'a is fighting back to expose the shadowy land grab.

But he is doing it in an unusual way — enlisting the services of an Israeli lawyer who spent 16 years as a municipal civil servant approving expropriations of Palestinian land in Jerusalem.

The lawyer, Stephen Berman, left his post as legal adviser to the Jerusalem municipality's real estate department and went into private practice in 2003. He is now using his inside knowledge of the system to expose what he says is the settler group's illegitimate property grab.

"This was my job, doing this stuff," the U.S.-born Berman told The Associated Press, recounting from behind his paper-littered desk the expropriations he used to approve. "That was their lack of luck."

Unlike some Israeli lawyers who fight for Palestinian rights in court, Berman is not an activist for the Palestinian cause. Shortly before he took on this case, he represented a Jewish settlement project in east Jerusalem.

"I don't care who the law serves," he said. "I care what the law is."

Following a paper trail of old maps and land registry documents, Berman said he uncovered how Israeli civil servants, stretching back decades, abused their power to seize control of the tiny but attractive triangle of real estate from the Abu Ta'a family in east Jerusalem and give it to Amana, a 40-year-old organization that spearheads the construction of Jewish settlements in east Jerusalem and the West Bank.

The organization, which has been investigated multiple times for fraudulent real estate deals, has helped plan and build numerous government-sanctioned Jewish settlements and unauthorized outposts.

An investigative program on Israel's Channel 10 TV in February reported that Israeli police investigated 15 West Bank land acquisitions where settlement outposts were built and found that Amana's subsidiary had forged documents for 14 of them. The subsidiary denied the claims.

"The Amana organization is a settler organization that deals with construction of settlements ... many times on stolen Palestinian land," said Hagit Ofran of the anti-settlement watchdog group Peace Now. "We are not surprised to see them stealing land also in Jerusalem."

"The trouble here is that the government is helping the settlers to take over this land," Ofran added.

A lawyer for Amana did not return repeated requests for comment, and reporters on a recent visit to the Abu Ta'as' plot were ordered out by an Israeli supervisor of the construction site.

Amana fenced off the plot in November and began building. There were no signs identifying the construction project or Amana, as required by law. The Jerusalem Municipality said in a statement that it would ask Amana to put up a sign.

"Having this land is our right," said Abu Ta'a. "We owned it for a long time, before Israel existed in this land."

The story began in 1967, when Israel captured and later annexed east Jerusalem, home to some of the city's holiest religious sites. The following year, to cement the annexation, Israel drew up a plan to expropriate large swaths of vacant Arab-owned territory along the line between east and west Jerusalem.

Some of the expropriated land went into building the Israeli national police headquarters, government ministries and large Jewish neighborhoods, which the international community considers illegal settlements. But some of the land slated for expropriation was left untouched for decades.

In 1989, planning officials approved a final planning scheme for the area. It was smaller than the original expropriation plan, and Abu Ta'a's plot was left out.

In 1991, the Israel Lands Administration, the government body that manages state-owned lands, declared in a court case that whatever land was needed was part of the new scheme. Berman said that gave the impression that Israel did not intend to take the Abu Ta'a plot.

As the attorney representing the city of Jerusalem, Berman was involved in that court case. When Abu Ta'a and approached him years later, in 2012, after learning his plot of land had been taken, Berman thought something didn't add up. "I started looking at the facts," Berman said.

He found that a year after the land authority gave the impression it was no longer interested in taking land in the area, officials quietly began doing the opposite. Eventually, the Abu Ta'a plot was transferred to the settlement group Amana.

Berman found documents showing that in 1992, just after the pro-settlement Likud party lost control of the government to a newly elected left-wing prime minister, the Lands Administration gave permission to Amana to start planning the construction of its headquarters on the Palestinian-owned land.

The lawyer said he believes this was a last-minute effort by pro-settlement land officials to push the land transfer through before then-Prime Minister Yitzhak Rabin could block it. Indeed, when the new government was formed, it froze the deal.

Then in 1997, a year after the pro-settlement Benjamin Netanyahu first became Israeli prime minister, the deal was revived and approved retroactively, Berman said.

At the time, Berman says, Amana secured the necessary approvals by tricking local and national land planning officials into thinking the land was owned by the government. The land authority did not respond to repeated phone calls and emails seeking comment.

But in 2005, when Amana tried to re-parcel the plot, it ran into a snag: the land was still not registered in the government's name.

To get final approval from Israel's finance minister, Israel Lands Administration officials "came up with a brilliant idea," said Berman.

They rezoned the map to make the Palestinian land look like it was connected to nearby government buildings. It made the expropriation look like it was for public reasons, Berman said, and it was approved. Abu Ta'a said his family has refused to accept an offer received in 2012 to apply for compensation.

After five months of court proceedings, a Jerusalem district court in March ruled that the planning scheme was done improperly.

But the judge ruled it was the result of a series of mistakes and stopped short of calling it fraudulent deceit, and therefore ruled that Amana could continue to build its headquarters.

Berman is now appealing to Israel's Supreme Court.

"Expropriation is sometimes a necessary and legitimate measure. In this case, there was a situation that was irregular," said Berman.