The Trump administration is set to defend its controversial decision to add a question about citizenship to the 2020 census in a closely watched federal trial that will begin Monday in New York City.

Controversy over the question immediately erupted when it was leaked that the Justice Department requested it in December so it could collect better data to enforce the Voting Rights Act. In March, Commerce Secretary Wilbur Ross, who oversees the Census Bureau, announced he had decided to add the question. Civil rights groups and other critics say the question is unnecessary and designed to scare immigrants and other minorities into not responding to the decennial survey. An inaccurate count would have severe and lasting consequences because census data are used to draw electoral districts and determine how hundreds of billions of dollars in federal funds are allocated.

The census currently asks about citizenship in the American Community Survey, a longer questionnaire that goes out to more than 3.5 million households each year. It has not asked about citizenship on its decennial survey ― which goes out to every American household ― since 1950. The Voting Rights Act, the basis for the Justice Department’s request to add the citizenship question, was passed in 1965.

The case, State of New York, et al. v. United States Department of Commerce, et al., is likely to focus on the way Commerce Department officials made the decision to add the citizenship question. The plaintiffs in the case ― 18 states, the District of Columbia, several cities and a handful of immigrant groups ― say the decision to add the question was motivated by discriminatory intent. They say the Justice Department’s request was a pretext and Ross was set on adding the question before DOJ asked the Census Bureau to do it and ignored evidence and recommendations that he should not add the question. The Commerce Department also made the decision to add the question without testing it ― an unusual practice given that questions are typically added to the census only after they’ve been extensively tested.

Agence France-Presse The Trump administration is defending a decision by Commerce Secretary Wilbur Ross to add a citizenship question to the 2020 census

The Trump administration says the question is not discriminatory and that Ross acted within his authority when he decided to add it.

While opening arguments are on Monday, the plaintiffs and the Trump administration have been fighting for months about how much information the government has to share about the decision. It’s easy to see why: The information the government has disclosed so far has substantially undermined its public justification for adding the question.

The emails show Ross eager to get the question on the census far in advance of the Justice Department’s request and getting frustrated that it was taking so long. He also disclosed in June that he had discussed adding the question with “senior administration officials” ― including Steve Bannon, ― and that it was he who approached the Justice Department about adding the question, not the other way around.

When he announced the decision, Ross downplayed concerns that the question would lead to a lower response rate. But a January memo from the Census Bureau’s top scientist warned that adding the question would be “very costly, harms the quality of the census count, and would use substantially less accurate citizenship status data than are available from administrative sources.”

Attorney General Jeff Sessions reportedly personally blocked the Justice Department from meeting with Census Bureau officials to discuss alternatives to adding the question.

John Gore, a top official in the Justice Department’s Civil Rights Division closely involved in the request, said in a deposition he didn’t know if the data collected through a citizenship question would be any better than the citizenship data DOJ already has.

The case is likely to eventually be decided by the Supreme Court, which has already weighed in twice in the case. It agreed to block Ross from having to sit for a deposition and answer questions under oath about adding the question. The Supreme Court on Friday also declined to halt the trial over a dispute on what evidence U.S. District Judge Jesse Furman, an appointee of Barack Obama, can consider in the case.

In addition to the New York case, there are lawsuits in California and Maryland challenging the citizenship question. The New York case is the first to proceed to trial.