It was interesting to read the New York Times report on Monday revealing the reasons behind the Swiss government’s destruction of evidence pertaining to a family of three Swiss engineers linked to AQ Khan’s global nuclear sales enterprise. The Tinner family—father Friedrich and his two sons Urs and Marco—were under investigation for helping orchestrate Khan’s sale of sophisticated nuclear technology to Libya and Iran; they were Khan’s key European intermediaries.

In their story, William Broad and David Sanger revealed the key reasons for the destruction: Pressure from the CIA to hide the role played by the Tinners in supplying them with information that ultimately led to the dismantling of Khan’s network. Broad and Sanger delve deeply into the Tinner case as an example of the tensions between two conflicting goals: First, to block nuclear proliferation; and second, to bring the key proliferators to justice. This presents a direct challenge to intelligence agencies, which are often unwilling to share how they gathered evidence on such operations.

These are themes that we explored in our hour-long radio documentary, “Business of the Bomb”, a collaboration with American RadioWorks, that aired on national public radio stations across the country last April and May.

In “Business of the Bomb,” ARW correspondent Michael Montgomery and I visited the South African end of Khan’s global operation, Tradefin Engineering, a factory outside of Johanessberg where a Swiss, a German and a South African trio of businessmen created key components for the Libyan enrichment facility purchased from Khan by Libya. Investigators found a videotape on the premises used by AQ Khan to advertise his capacity to build, on demand, nuclear enrichment and bomb-making facilities. (We obtained exclusive access to that tape, and present an audio excerpt here; you’ll hear the voice of AQ Khan himself pitching to others his success at building Pakistan’s nuclear arsenal).

In the Tradefin case, the US Department of Energy refused to cooperate with South African authorities in a public trial due to their concerns about revealing intelligence sources and methods. The result? South Africa’s ultimately unsuccessful effort to keep the trial secret established an important principle of openness in that country, and, some in South Africa suspect, led to lighter sentences for the principle players, none of whom ultimately had to serve time in prison. “I’d rather not discuss that,” said the DoE’s head of non-proliferation James Tobey, deputy undersecretary for nuclear non-proliferation at the Department of Energy’s National Nuclear Security Administration when we asked him about the case.

Back in March, up to the last minute before recording our narration, we were trying to confirm the Swiss destruction of evidence in the Tinner case, which I’d learned from an anonymous tip. The tip was confirmed by Margrit Meyer, chief assistant to Swiss Federal Magistrate, who said that the evidence had been destroyed as the case was transferred from the Swiss Attorney General’s office to that of the Federal Magistrate for further investigation “Some evidence is not there anymore,” she told me in a March telephone interview from her office in the Swiss capital of Berne. Meyer refused to identify the nature of the evidence or how or why it was destroyed.

I was astounded to see that his U.S. address was that of the CIA in Washington DC. His given phone number was the CIA switchboard in Langley, Virginia. His title was “Agent.”Two months later, in May, Switzerland’s President, Pascal Couchepin, announced to the world that the Tinner files, including nuclear bomb designs, had been destroyed. Now Broad and Sanger have added considerable rich detail suggesting it was the United States which requested the file’s destruction “less to thwart terrorists than to hide evidence of a clandestine relationship between the Tinners and the CIA.” The three men, they report, received at least $1 million in payments from the agency for their inside tips on Khan’s operation.

One other point of interest to a story that no doubt will continue to unfold: When we were conducting our final reporting back in March, I researched Urs Tinner—the one of the three considered most deeply involved in Khan’s illicit enterprise—through the electronic database Accurint. I was astounded at the time to see that his U.S. address was that of the Central Intelligence Agency in Washington DC. His given phone number was the CIA switchboard in Langley, Virginia. His title was “Agent.” This seemed so outlandishly brazen at the time that I didn’t trust it, that such a secret could be hidden in such full sight (with the help of a subscription to Accurint). Congratulations to Broad and Sanger for confirming the long and extraordinary story behind that address.

Mark Schapiro specializes in international and environmental stories. His award-winning work appears in all media: in publications such as Harpers, The Atlantic, Mother Jones and Yale 360; on television, including PBS FRONTLINE/World and KQED; on public radio including Marketplace; and on the web. He is currently writing a book for Wiley & Co. investigating the backstory to our carbon footprints. His previous book, "EXPOSED: The Toxic Chemistry of Everyday Products and What’s at Stake for American Power," reveals the health and economic implications of the tightening of environmental standards by the European Union.