J-Source's Investigative Journalism editor Cecil Rosner brings us a special dispatch from the Global Investigative Journalism Conference in Kiev: What it was like for the investigative journalists who worked with Julian Assange, and why one will never do it again.

J-Source's Investigative Journalism editor Cecil Rosner brings us a special dispatch from the Global Investigative Journalism Conference in Kiev: What it was like for the investigative journalists who worked with Julian Assange, and why one will never do it again.

"I personally would not work with Julian Assange or WikiLeaks ever again."

That was the blunt judgment of David Leigh, investigations editor at The Guardian and one of the original mainstream media partners with the whistleblowing website. "He is impossible to work with. Hackers and journalists don't really mix."

Leigh was one of four journalists who described their techniques, strategies and frustrations in dealing with WikiLeaks during a fascinating panel discussion Thursday at the Global Investigative Journalism Conference in Kiev.

Journalists at the New York Times, the Guardian, Oslo's Aftenposten and Nigeria's Next newspaper were all involved in trying to analyze and verify thousands of documents dealing with U.S. diplomatic traffic and war reports. It forced all of them to develop new methods so they could make sense of such a massive dump of raw information.

"For an old man like me, having to deal with all that data was something new," said Leigh. The Guardian was handed four massive datasets, and one of the newspaper's first steps was to build a searchable database of the documents.

The newspaper quickly realized that there were many important revelations, but that not everything in the documents was true. Verifying, analyzing and weighing the evidence became the most important exercise. It turned out that some of the documents labelled Secret or designated as not for foreign eyes were less interesting than cables merely coded as confidential.

"The old skills of journalism I learned as a young man are still relevant," Leigh added, noting that follow-up freedom of information requests were important in verifying some of the stories.

The original five media partners working with WikiLeaks weren't unanimous in their assessment of the cables. Leigh said Bill Keller of the New York Times accused the Guardian of being too focused on stories dealing the war dead because of its left-wing leanings.

Leigh eventually fell out with Assange over disagreements about how the material was handled and Assange's objections to the Guardian's coverage of sexual assault allegations in Sweden, among other things.

Andy Lehren, one of the key New York Times journalists working on the material, said his initial assignment was to analyze the documents and look at a one-day story. The newspaper ultimately formed a large, secret team to make sense of the material, much of which constituted single-source stories and incomplete accounts, he said.

The Times brought in other datasets, such as a database of private security contractors, to  compare to the WikiLeaks documents. In some cases,  a single cable told an entire story, but in many other instances it was necessary to do considerably more analysis and reporting.

Lehren said the diplomatic cables continue to live on, providing more insight as new world developments take place. He still spends time sifting through and reading them regularly.

Jan Gunnar Furuly, with Oslo's Aftenposten, said his newspaper managed to get the full set of diplomatic cables without entering into a formal relationship with WikiLeaks. "Thanks to a genius guy in our IT department" the newspaper had a searchable database operating within short order, enabling journalists to search for relevant documents.

The newspaper then formed a coalition with about 75 European journalists so the material could spread as widely as possible. Aftenposten printed important stories that the major WikiLeaks partners hadn't yet touched.

Musikilu Mojeed, of Nigeria's Next newspaper, received exclusive access to the Nigeria-related WikiLeaks cables in February of this year. He said they adopted a cautious and skeptical approach, treating the cables not as gospel truth but as the basis for further research and interviews. Providing additional context was an important objective for each report.

Though the leaks led to several major scoops and revelations, Mojeed acknowledged that they blundered by reporting a claim from a cable that their president had voted four times in the 2007 election. This subsequently turned out to be false, and the newspaper had to cover its face in shame for the error, he said.

Leigh and Lehren both said pressure from the U.S. State department and other government officials did not force them to back down on printing any important stories. While both were careful to protect identities of sources named in the documents, they didn't suppress pertinent information only because it was embarrassing to some.

Leigh said the newspaper was asked not to publish anything on the situation in Yemen because of the sensitive state of affairs there, but he paid no heed. Mojeed added that some officials in the Nigerian administration wanted inside information on the contents of the documents, even offering to pay for it.

Despite the treasure-trove of information, and weeks of exclusive reports filed by all the newspapers, there were many strained relationships along the way. Leigh left no doubt about his disdain for Assange's tactics and ethics.

"He tried to double cross us over and over again."

More than 500 journalists are at the conference. Assange was invited, but did not attend.