A landmark fraud trial opened Monday for Spain's Princess Cristina, accused of helping bankroll a lavish lifestyle with funds her husband received from an alleged scheme to embezzle millions from public contracts for conferences and sporting events.

Cristina and her husband, Inaki Urdangarin, said nothing to dozens of reporters as the couple entered a makeshift courthouse amid tight police security aimed at keeping anti-monarchy protesters away.

The two then sat silently among a group of 16 other defendants as a judge read out the charges for the historic trial, which marks the first time that a member of Spain's royal family has faced criminal charges since the monarchy was restored in 1975.

Urdangarin and other are accused of embezzling up to $6.8 million from contracts which were inflated or never performed.

The 50-year-old Cristina faces two counts of tax fraud, carrying a maximum prison sentence of eight years, for allegedly failing to declare taxes on personal expenses paid by a real estate company she owned with Urdangarin, an Olympic handball medalist turned businessman.

He faces more serious charges of using his former Duke of Palma title to land public contracts from politicians through the nonprofit Noos Institute he ran with an associate.

Authorities Monday morning detained one protester with an anti-monarchy flag a short time before Cristina showed up at the court inside a sedan with dark tinted windows. A small group was allowed to protest nearby after the proceedings began.

Thousands of anti-monarchy protesters staged noisy demonstrations in 2014 while Cristina answered questions about the case posed by an investigative judge.

One of her lawyers argued in court Monday that a Spanish legal precedent should be applied to her case that allows tax fraud cases to be dropped when they are not initiated by prosecutors.

The lawyer, Jesus Maria Silva, urged the three-member panel of judges to drop the charges she faces because prosecutors don't believe she committed a crime. The case against her is happening under a quirk of Spanish law allowing private groups to pursue criminal charges.

The judges were expected to suspend the court proceedings late Monday or Tuesday so they could decide whether the princess will remain charged and required to appear again in the court when testimony begins in February.

The same defense tactic can't be used by Urdangarin, meaning it's all but inevitable that details will come out during the proceedings about the couple's everyday life behind the high walls of the mansion they were forced to sell during the investigation.

There are so many defendants and lawyers — plus reporters — covering the case that judicial officials move the trial from a courthouse to a sprawling building complex on the outskirts of Palma de Mallorca normally used to hold mass training courses for public servants.

The case is being heard in the regional capital of Spain's Balearic Islands because many of Urdangarin's business deals under investigation were for the islands.

Cristina denied knowledge of her husband's activities during the 2014 closed door court appearance, but judge decided she could be charged with tax fraud in 2007 and 2008.

Her case was driven forward by the anti-corruption group Manos Limpias (Clean Hands).

Details about the couple's lifestyle — including parties paid for by the real estate company at their modernist Barcelona mansion, salsa-dancing classes and vacations at expensive hotels — emerged from the pre-trial investigation, outraging Spaniards as the country teetered on the edge of an economic crisis.

The case added to the stream of bad headlines for Cristina's father, former King Juan Carlos — already smarting from a backlash after he broke his hip during a 2012 elephant hunting trip seen as an example of royal excess. Juan Carlos abdicated in 2014, saying Spain needed fresh royal blood.

On taking the throne, King Felipe VI — Cristina's brother — pledged to restore public trust in Spain's monarchy. He later stripped Cristina and her older sister Princess Elena of their roles as official members of the royal family though they have not given up their slots of succession in line for the throne.

The trial is expected to last six months.