LONDON—Cambridge Analytica has been found guilty of breaking data laws after refusing to disclose how much information it holds on an American professor, where it got the data, and—perhaps most importantly—how it used it and who it gave it to.

The British analytics firm, which was hired by the Trump campaign, has been accused of misusing the Facebook data of almost 100 million Americans while working to elect President Trump.

Prof. David Carroll, at the Parsons School of Design in New York, filed a formal request to see what data was held on him after reading about Cambridge Analytica’s role in the 2016 presidential election. Under British data laws, companies are required to disclose what they hold on any individual who makes such a request.

SCL Elections, a parent company of Cambridge Analytica, confirmed it did have data on Carroll, including detailed metrics on his political views, specifically how he was likely to vote and which hot-button issues like gun rights or immigration would motivate him.

The existence of this predictive table suggested Cambridge Analytica must have gathered a large volume of data on the media professor, prompting Carroll to ask where it had come from and with whom it had been shared?

Facebook later admitted that Cambridge Analytica had access to personal data on up to 87 million people, mostly in the U.S. The company collapsed in 2018 after undercover reporters caught its executives bragging about electoral dirty-tricks operations, including the secret use of proxy organizations and super PACs to buy ads targeted at individuals in the U.S. that could not be traced back to the Trump campaign.

SCL Elections refused to provide further information to Carroll, claiming that because he was American, and outside British jurisdiction, he had no more right to the data “than a member of the Taliban sitting in a cave in the remotest corner of Afghanistan.”

Britain’s Information Commission disagreed, and issued a compliance order that would make it illegal for SCL or Cambridge Analytica to continue to rebuff Carroll’s efforts.

In court Wednesday, the administrators of SCL Elections, which declared bankruptcy in May last year, finally admitted that it had broken the law. The last-minute guilty plea came on the day the trial was scheduled to begin.

The judge ruled the company had shown a “willful disregard” for the enforcement of data laws, but sentenced the company to pay less than $20,000—even with the addition of some of the costs, the penalty was around $26,000.

There was no suggestion the administrators will now grant Carroll’s request for access to the full data on him. That information is held on computers seized from Cambridge Analytica by the ICO, and stores around 700 terabytes of data, which the court was told equated to around 81 billion pages of information.

Ben Summers, for the prosecution, admitted that finding the information on Carroll was like searching for a needle in a haystack. “But it was obvious to the ICO that in order to deal with the needle, you had to have access to the haystack.”

The court was told Wednesday that Cambridge Analytica and its related companies had not provided the relevant passwords to the ICO to access that data, but the administrators had now done so. That means the British watchdog may eventually be able to work out what data was gathered on Carroll and millions of fellow American voters, and how it was used—by a company that boasted of its dirty tricks—to help Trump win in 2016.