Court officials said that Javier Martin-Artajo declared in court that he would fight extradition to face charges of fraud and falsifying bank records to hide the extent of losses in early 2012 that eventually totaled about $6 billion.
Martin-Artajo turned himself into Spanish authorities on Tuesday. He is a resident of London, where the trades took place. But he is a Spanish citizen and Spain rarely forces its citizens to face charges in other countries, CNNMoney reported.
A retired judge who requested anonymity told CNNMoney that Martin-Artajo may have returned to Spain knowing that would decrease the odds that he would have to stand trial.
In court, Martin-Artajo said the charges against him were false. Authorities in the United States said the false bank records caused JPMorgan Chase to underestimate losses in a quarterly financial statement by hundreds of millions of dollars.
Martin-Artajo was charged along with Julien Grout, who reported to him in the London office.
The trader who placed the bets, Bruno Iksil, known as the London whale, was not charged, as he is cooperating with authorities.
The United States has 40 days to request Spain hand over Martin-Artajo to U.S. authorities. The Spanish court ordered the former banker to stay in the country and to make an appearance in court twice a month.