The party, with 78 of 735 seats in Germany's parliament, leads polls in several poorer, post-industrial eastern states where its anti-establishment, anti-immigrant stance resonates. It opposes Germany's backing for Ukraine in the war with Russia.
"At no time was I disadvantaged because of my ethnicity in the party or deprived of my rights," said Meysam Ehtemai, a former mayoral and parliamentary candidate who described himself as a "German citizen of Persian roots".
The BfV's lawyer Wolfgang Roth said the testimony on Wednesday of the three members - Ehtemai, German-born Athanasios Robert Lambroug, son of a Greek immigrant, and Nigerian-born Catherine Ajagun Schmiedel - had little bearing on the preponderance of evidence.
"The plaintiffs distinguish clearly between legal citizenship and an ethnic German people," he said. "The state is defined in legal terms, the people in ethnic terms."
AfD politician Roman Reusch responded: "Imagine trying to explain that hair-splitting to simple people!"
Leading figures in the party have warned against Germany's "Africanisation", called migrants "invasive species" and dismissed as "passport Germans" naturalised immigrants.
"I got interested in politics after I noticed how Germany was changing with mass immigration, and as a mother I was concerned," said Ajagun Schmiedel, who contrasted her "safe place" in the AfD with social media, where she said she had been called a "Black Nazi".
Originally due to wrap up in two days, the hearing had to be adjourned to an unspecified future date thanks to a flurry of AfD filings - dismissed by adversaries as stalling tactics - asking if the BfV had planted agents in its leadership.
AfD lawyer Michael Fengler read out motions asking for testimony on whether "sources, spies, agents provocateurs, undercover agents, informants or concealed employees in the plaintiff's leadership", changing the name only of the official he wanted to summon.
No evidence was presented that the BfV had done so. AfD lawyers also asked if the BfV had spied on case preparations, which it denied.
'DELAYING TACTICS'
For the BfV, Roth called the questions "out of the blue" and "delaying tactics". When judge Gerald Buck said the motions should be submitted in consolidated form later, the AfD accused him of bias and demanded his replacement.
The case, titled "AfD vs Federal Republic of Germany", attracted so much media and public interest that the hearing had to be moved to the foyer of the court in the city of Muenster, where they were watched over by a Korean artist's two giant statues of squatting men.
The party, which has moved increasingly to the right, portrays itself as the target of a complacent, self-serving establishment it stands ready to sweep away.
The BfV, which has the power to monitor perceived threats - from foreign agents and neo-Nazis to Communists and racist, violent or anti-democratic groups - has since 2021 viewed the AfD as a "suspected extremist" organisation.
A ruling against the party would do little to deter core supporters but could put off wavering voters in upcoming European elections if spooked by allegations of extremism.
