SAN FRANCISCO — The Latest on a trial in California over the Trump administration's decision to add a citizenship question to the 2020 U.S. Census (all times local):

11:15 a.m.

An expert in surveys says adding a citizenship question to the U.S. Census would worsen the undercount of Latinos and non-citizens compared to other population groups.

Colm O'Muircheartaigh (Co-LUM Oh-Merc-a-TAY) testified on Monday at the start of a trial in San Francisco before a federal judge. Judge Richard Seeborg is scheduled to hear a week of testimony. The judge will decide whether to allow the question.

O'Muircheartaigh was a witness for California and the other plaintiffs in the case. He said a citizenship question would reduce the percentage of Latinos and households with non-citizens who respond to the Census questionnaire. He said additional efforts by the Census Bureau to count those people would not be enough.

The U.S. Department of Justice says Census officials take steps to guard against an undercount.

Seeborg is the second federal judge to hold a trial on the issue. A ruling in a trial in New York that ended in November is expected soon.

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10 p.m.

A trial will begin in federal court in San Francisco over the Trump administration's decision to add a citizenship question to the 2020 U.S. Census.

Judge Richard Seeborg is scheduled to hear a week of testimony starting Monday. The judge will decide whether to allow the question.

Seeborg is presiding over lawsuits by California and numerous cities in the state that argue the citizenship question would discourage immigrants and Latinos from participating in the Census.

The plaintiffs say that would result in an undercount that would jeopardize their federal funding and the state's representation in Congress.

The U.S. Department of Justice argues Census officials take steps to guard against an undercount.

Seeborg is the second federal judge to hold a trial on the issue. A ruling in a trial in New York that ended in November is expected soon.