The criminal case against two former JPMorgan Chase & Co (JPM) - Get Report traders who were accused of concealing billions in losses was closed in U.S. court after a key witness known as the "London Whale" pointed fingers at the bank's top executives, the Wall Street Journal reported.

The London Whale, whose real name is Bruno Iksil, said the bank's CEO Jamie Dimon and his executives were responsible "much, much more than [Iksil's] two colleagues could ever be." The two, Javier Martin-Artajo and Julien Grout, faced charges for their roles in a 2012 trading debacle that cost JPMorgan over $6 billion.

Prosecutors in the Manhattan U.S. attorney's office filed a motion in federal court July 21 to drop the charges against Martin-Artajo and Grout, citing Iksil's inconsistencies in testimony, noted the Journal. The criminal case was closed, but civil charges brought forth by the Securities and Exchange Commission are pending.

Iksil said the debacle started when senior managers instructed traders to reduce positions in riskier assets to meet new regulatory demands, which eventually led to the losses in question. Dimon gave a public presentation in 2010 that promoted this strategy, though he never gave an explicit order, Iksil said, according to the Journal.

Shares of JPMorgan are lower in late morning trading.

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