JPMorgan Chase Chairman and CEO Jamie Dimon should keep both roles because of the banking giant's "incredible return" since last year's "London Whale" fiasco, management expert Jeffrey Sonnenfeld told CNBC on Thursday.
Ahead of this month's annual meeting, Dimon, who wants to keep both jobs, is facing pressure from shareholder advisory firms Institutional Shareholder Services and Glass Lewis, which are calling for the chairman and chief executive officer posts to be split.
Both firms said the bank's $6.2 billion London trading losses, disclosed in the spring of 2012, showed that the JPMorgan board failed in its oversight of company executives.
(Read More: Warren Buffett to CNBC: Dimon Should Keep Both Jobs)
Sonnenfeld, a senior associate dean at the Yale School of Management, called the trading disaster "a mistake."
"Anyone in business is going to have an error. It was an honest error," he said in a "Squawk Box" interview. "Look how they've recovered from it: record profits."
He also cited Dimon's response to the fallout, including going before Congress to answer questions about how the losses happened.
JPMorgan stock had been trading in the mid-40s ahead of the scandal. It dropped sharply and bottomed out in June around $31 a share.
"Now we're up around $50. It's an incredible return," Sonnenfeld said. "[Dimon's] just being made a scapegoat."
In an op-ed in Thursday's New York Times titled "The Jamie Dimon Witch Hunt," Sonnenfeld wrote: "While the model can work on occasion, it is surely no panacea that ensures good economic results or good governance. Last spring saw a record of 56 shareholder votes on leadership-role separation—with only four approved. This year looks to be similar."
In addition to JPMorgan, he wrote that Disney, Boeing, and DirecTV are being pressured to split the leadership roles, despite the "excellent returns" the leaders of those companies have delivered to shareholders.