Immediately after taking the stand, Cristina invoked her right to answer only questions posed by her own lawyer.
She then sat and listened silently – but didn't respond to – questions posed by a lawyer for the group that leveled the tax fraud charges against her.
The Infanta Cristina, as she is often known in Spain, then answered only the questions posed by her own lawyer during a tense 20 minute session.
Princess Cristina de Borbón, 50, the first member of Spain's royal family ever to be put on trial in a criminal court, is charged with tax fraud as part of an alleged $6 million embezzlement scheme involving her husband and 16 other defendants.
Cristina and her husband, Inaki Urdangarin, 48, both deny any wrongdoing. The other defendants also maintain their innocence.
The princess faces eight years in jail if the three-member panel of judges finds her guilty.
She told the court that she had never asked her husband, who is an Olympic handball medalist, about the minutiae of Aizoon, a property company they jointly owned.
"At that time my children were very small and we were very busy. He was in charge of the family expenses. I didn't get involved in that," the princess said.
Asked by her own attorney why she never talked with her husband about what the company did, Princess Cristina said that these "weren't issues that interested me".
The princess said she "didn't know" why some costs for the couple's lavish lifestyle, including an African safari and more than $1,100 for wine were charged to a credit card for a company they co-owned.
The case began in 2010 and has become highly charged because many believe it symbolizes perceived corruption among Spain's elites – including the royal family.
King Felipe stripped his sister and her husband Inaki Urdangarin of their titles, the Duke and Duchess of Palma de Mallorca, in 2015.
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Princess Cristina now lives in Switzerland, but remains the sixth in line to the Spanish throne.
Earlier this week Urdangarin, King Felipe's brother-in-law, told the court that the Royal Household filed Princess Cristina's tax returns and contended that his company was set up to "channel his fees."
He also claimed that he never acted without first running things by the princess’s adviser in the Royal Household, Carlos García Revenga.
"I didn’t take a step in my life without consulting with García Revenga, so that he was informed about what we were doing," Urdangarin told the court.
The Infanta Cristina is accused of making personal use of Aizoon's corporate funds to pay for clothes and dance lessons for the couple's children, as well as work on the their Barcelona mansion, where the couple lived with their four children.
They were subsequently forced to sell the property as their legal troubles mounted.
The couple's lavish lifestyle was funded from corporate money siphoned off to reduce the firm's taxable profits, prosecutors contend.
Her husband is alleged to have used the non-profit Noos Institute sports foundation as a vehicle to win falsely inflated contracts from regional government bodies, before channelling the money to personal accounts via tax havens.
Noos is alleged to have received more than $6 million of public money.
The trial will continue later this month.