AILSA CHANG, HOST:
We're going to turn now to Larry Johnson. He spent 24 years as a U.S. Secret Service special agent, including turns supervising the presidential protection division and the criminal investigation division. Welcome to the program.
LARRY JOHNSON: Thanks for having me, Ailsa.
CHANG: So two of these explosive devices were reportedly intercepted by the Secret Service. What does that mean? I mean, how close were these devices from reaching their intended targets?
JOHNSON: Well, Ailsa, the common practice of the Secret Service is to screen mail at an off-site location, typically - and this has been going on for the last 30, 35 years - where they have available a number of different sensors that detect biosensors, radiation and other known gases. And in this case, if it was a pipe bomb, it would have been easily detected in an X-ray machine or a trace detection machine on-site.
CHANG: That's just what I was going to ask you - if you could give us a picture of what that mail-sorting process is like. I mean, when Secret Service agents sift through the daily mail, how do they handle it in case it could explode or be toxic? You mention an X-ray machine. What else?
JOHNSON: Typically if it's determined that it's of risk, if it's a device that's suspicious, they have containers. They also have - they have robots that will come in and actually look at the device remotely so that there's not a human involved in the examination process. So it's very detailed. The Secret Service actually goes through exercises where their own try to place devices that might be at risk and test the mail operation 24/7.
CHANG: Now, who else has their mail screened by the Secret Service? Besides current officials and former presidents, who else enjoys this kind of protection?
JOHNSON: Well, anybody under the protection of the United States Secret Service - so foreign leaders if they come to this country - if it's the leader of that country, then they get the same level of protection, which involves screening. It's a layered security approach. So there's outer perimeters, middle perimeters and inner perimeters. Everything that comes in and out...
CHANG: Right.
JOHNSON: ...Of a secure location gets screened, whether it's humans, whether it's vehicles, whether it's packages or equipment. Everything is screened. And actually, a lot of large corporations follow that same process.
CHANG: But the devices that we've been discovering today, that we've been reporting on today - the ones intended for other targets like former CIA Director John Brennan or former Attorney General Eric Holder - those devices would not have been caught by the Secret Service. That's correct, right?
JOHNSON: That is correct. And I actually do some consulting to high-net-worth VIPs, even political types that are advised to not receive mail at their homes and to receive mail at an off-site. The Post Office will hold and screen at special request. So there are things that you can put in place if you're just an average citizen that doesn't have the Secret Service at your disposal.
CHANG: That's Larry Johnson, former Secret Service agent. Thanks very much.
JOHNSON: Thanks, Ailsa. Transcript provided by NPR, Copyright NPR.
