SPANISH police arrested the leader of an anti-corruption group that brought criminal tax fraud charges against Princess Cristina, an official said, as more testimony was heard in the royal’s historic trial.

Miguel Bernad, leader of the Manos Limpias (Clean Hands) group, was taken into custody by financial crimes officers at his Madrid home, according to a Spanish police official, who spoke on condition of anonymity because of police policy.

A separate police statement said 11 people were arrested in an investigation focusing on whether Manos Limpios had filed charges in some cases only to withdraw them later in return for money. The statement did not mention Cristina’s case.

But that trial is now taking place because Manos Limpios pursued tax fraud charges punishable by up to eight years in prison against Cristina, the sister of King Felipe VI. Prosecutors had declined to do so, saying Cristina should face an administrative fine at most. Due to a quirk in Spanish law, private groups like Manos Limpios can initiate criminal cases when authorities decide not to but a judge must agree the case can go forward. One did in 2014.

The Manos Limpias lawyer questioning witnesses in Cristina’s case, Virginia Negrete, told reporters in Palma de Mallorca where the trial is underway that she had no information about Bernad’s arrest and was unaware of any alleged possible pay-off for the withdrawal of charges against Cristina.

“I’ve never asked for money in my professional career in this case or in any other,” she said. “I have a clean conscience and very clean hands.”

Negrete spoke overnight after Francisco Camps, the former leader of Spain’s Valencia region, was questioned in court about events set up by Cristina’s husband in the region.

The landmark fraud trial started in January, with Cristina appearing in court and answering questions as the first member of Spain’s royal family facing charges since the monarchy was restored in 1975.

Cristina is accused of failing to declare as income personal expenses paid by a real estate company she owned with her husband Inaki Urdangarin, an Olympic handball medallist-turned-businessman. Urdangarin, in the same trial, faces charges of embezzling up to 6.2 million euros ($9 million) from contracts for sports conferences and events that were allegedly inflated or never performed.

The princess’ husband, formerly the Duke of Palma, is accused of using his title to land the deals for the non-profit Noos Institute he ran with business partner Diego Torres.

Lawyers for Cristina, Urdangarin and Torres say they are innocent.

Immediately after taking the stand in March, Cristina invoked her right to answer only questions posed by her own lawyer. She testified that her husband handled all bill payments for the couple and she didn’t know why some costs for their lavish lifestyle including an African safari and more than 1000 euros ($1500) for wine were charged to a credit card for a company they co-owned. The princess’ lawyer aimed to distance her from involvement with Aizoon, the real estate consulting company Urdangarin ran from an office inside the Barcelona mansion they lived in for years with their four children but were forced to sell as their legal troubles mounted.

Money went from Noos to Aizoon, which Urdangarin and the princess testified was set up to receive his income.

A three-judge panel hearing the case will weigh whether the couple abused Aizoon, described in court papers as a “front company” that may have funded luxury vacations and parties at the couple’s modernist mansion.

Urdangarin testified he made Cristina a co-director of Aizoon because he wanted her to be part of the business project but also insisted “she didn’t have anything to do with the company’s activities.” The questioning of witnesses is expected to continue through June. Cristina and her husband were not in court Friday and have not been during witness questioning because their presence is not yet required.