NEW YORK ― In December of last year, John Abowd, the top scientist at the Census Bureau, quietly scrambled with his team of researchers to complete an analysis that was a high priority for his bosses.

The Department of Justice, claiming it wanted better citizenship data, had requested earlier that month that the 2020 census include a question about citizenship status. Abowd and his researchers ― he referred to them as his SWAT team ― were trying to figure out the impact of adding the question to the decennial survey.

In mid-January, Abowd’s team sent their findings to Commerce Secretary Wilbur Ross, who oversees the Census Bureau and would ultimately decide whether to add the question. Their conclusion was clear: Adding a citizenship question to the census was not a good idea. It would be costly and harm the accuracy of census data, Abowd wrote, because fewer people would choose to voluntarily respond to the survey. Instead, he recommended using existing administrative records to get citizenship data that the Census Bureau could then provide to the Justice Department.

Top Commerce Department officials sent Abowd a series of questions about his findings and he met with Ross to discuss his memo in February. On March 26, Ross announced he was adding the citizenship question anyway.

Over the last few weeks, Abowd played a key role in a closely watched federal trial in New York City challenging Ross’ decision. In one of several such suits filed around the country, the plaintiffs ― 18 states, the District of Columbia, several cities and a handful of immigrant groups ― say a judge should block the Trump administration from adding the question because Ross was predisposed to add it even before the Justice Department made its request and his decision was “arbitrary and capricious.”

Over the course of the trial, which began Nov. 5 and concluded Tuesday, the plaintiffs sought to show that Ross ignored hard evidence and hid what they allege is the Trump administration’s true motive for trying add the question: It wanted to decrease the response rate among Hispanic people and noncitizens.

Bloomberg via Getty Images Commerce Secretary Wilbur Ross has come under fire over his decision to add a question on citizenship status to the 2020 census.

The trial has huge stakes because an inaccurate census would have huge consequences. Census data is used to determine how electoral districts are drawn and how many congressional seats each state gets. The data is also used to determine the allocation of hundreds of billions of dollars in federal funds.

During the trial, neither Abowd nor anyone else presented much hard evidence that adding the citizenship question to the 2020 census was smart. Early in his testimony, Abowd was asked was whether it was true he and other top officials agreed that adding the citizenship question was not a good idea. Without hesitating, he said that was correct.

Without much hard evidence in favor of adding the question, Department of Justice lawyers presented a kind of shuffling defense. Regardless of whether adding a citizenship question was good policy, they argued, it was Ross’ decision to make and the courts do not have the power to evaluate a policy and determine if there was a better one. Besides, they claimed, Ross did conduct a careful review.

And even though the evidence Abowd found showed adding a citizenship question wasn’t a good idea, Justice Department lawyers said there wasn’t concrete evidence that adding the question alone would cause a more inaccurate overall count. They insisted that the bureau’s efforts to follow up with people who chose not to self-respond would mitigate any drop in the number of people who did not voluntarily respond.

The plaintiffs repeatedly pointed out Ross took the unusual step of adding the citizenship question without testing it out first, which is why it was so hard to come by evidence assessing the direct impact of the change.

The Washington Post via Getty Images Critics say President Donald Trump's administration wanted to add a citizenship question to the 2020 census to decrease the response rate among Hispanic people and noncitizens.

Regardless of whether the citizenship question ultimately ends up on the census, the trial was damaging to the Trump administration. After Ross repeatedly said he considered adding the citizenship question after the DOJ’s request, he disclosed in the lawsuit that he’d wanted to add it months beforehand. The Justice Department didn’t seek on its own to add the citizenship question: Ross revealed that he approached the agency and solicited the request.

In fact, months before the DOJ asked for the citizenship question, Ross expressed frustration to a top Commerce Department official that nothing was being done to get the question on the census. It was also revealed that Steve Bannon, then working in the White House, and Kansas Secretary of State Kris Kobach, who favors adding the citizenship question, had Ross’ ear as he considered the addition.

Nor did some of the Trump administration’s best talking points in favor of adding a citizenship question hold up very well under scrutiny. The administration has pointed to the fact that the Census Bureau already asks people about citizenship on the American Community Survey, which goes out to millions of households each year. But when the bureau compared responses on that survey with those for the decennial census, which goes to every American household, they found that the response rate decreased more steeply among households with at least one noncitizen compared to households that were all citizens. Census experts also discovered that noncitizens were inaccurately identifying themselves as citizens on the annual survey about 30 percent of the time, an issue Abowd said the bureau was previously unaware of and evaluating.

The Justice Department’s original rationale for adding the question also got weaker during the trial. John Gore, the head of the civil rights division when the department made its request, said in a deposition in the case that he did not know if the data resulting from adding a citizenship question would be any more accurate than what the DOJ currently has available.

The Justice Department also repeatedly sought to block U.S. District Judge Jesse Furman from proceeding with a trial at all. Since Labor Day weekend, the Justice Department submitted over a dozen requests to Furman and appeals courts, including the U.S. Supreme Court, to delay the trial. The DOJ challenged what evidence Furman should be able to consider in the trial and said the proceedings should be put on hold until the Supreme Court weighs in. The repeated requests clearly irritated Furman, who ripped Justice Department lawyers when he denied their most recent request to delay the trial, saying “enough is enough.”

On Tuesday, Brett Shumate, a Justice Department lawyer, asked that should Furman rule against the Trump administration, he limit the scope of his remedy only to affect the parties that would be injured and allow the Commerce Department to decide how to implement it. When Furman asked if that would mean a citizenship question could be asked in some states and not others, Shumate said that would be up to the commerce secretary to decide. Lawyers for the plaintiffs immediately blasted the suggestion as ridiculous, since asking different questions in different states would defeat the entire purpose of the survey ― getting consistent and comprehensive information about as many Americans as possible.

Throughout the proceedings, Furman indicated he wanted to move the trial along quickly because the Census Bureau is approaching hard deadlines in its preparations for the 2020 census. He ended Tuesday’s proceedings by saying he would aim to get a ruling out in the next few weeks.