It’s been just a week since the death of Alexander Litvinenko, the former KGB agent and recent vocal critic of Russian President Vladimir Putin, whose murder by radiation poisoning has yet to be solved, but the intrigue surrounding the case becomes ever greater. On Thursday, the FBI announced that it would join the investigation, and British authorities say they’ve found traces of radioactivity in a dozen sites around London, including five planes, some reportedly used for a Moscow-London route. Additionally, another Putin critic, Russia’s former acting prime minister Yegor Gaidar, has fallen mysteriously ill while in Ireland for a conference. As of this writing, no cause for Gaidar’s illness had been determined.

Litvinenko’s murderer has not been found, but the poison that killed him has: polonium-210, an isotope of polonium, an element first discovered by Marie and Pierre Curie and named for Poland, Marie’s native country. Used as part of the trigger in the earliest atomic bombs, including those dropped on Japan, polonium-210 is a highly radioactive substance. The alpha particles it emits can be lethal when absorbed into the human body.

Salon spoke with John Large, who spent some 20 years as a research fellow with the British government’s Atomic Energy Authority before starting his own firm, Large & Associates, where, among other things, he was responsible for risk analysis during the salvage of the sunken Russian nuclear submarine Kursk. Large told Salon he believes the poisoning of Litvinenko was too sophisticated — potentially involving radical innovations like nanotechnology — to be the work of anyone not connected with a state. He also thinks the sushi that has been the focus of public speculation about the case may not have been the means used to kill Litvinenko.

Who could produce this amount of polonium-210?

Polonium, although it does occur naturally, is at the very end of the uranium decay train.

You need a nuclear reactor, you need a radiochemical laboratory that can handle radioactive material, and then you need a clinical laboratory that can cut it into a designer drug. Now, those facilities are simply not available in other than state enterprises. So countries like the United States, the Russian Federation, Britain, France and Israel are the sort of countries that can do this.

So this isn’t something that a well-equipped chemistry professor could do.

No. The other point is this: Let’s assume it was an assassin. The assassin has to work backwards. He has to know when the victim is going to be available for dosing, and he has to work backwards to know when the material is coming into the country, how it’s coming into the country, when it’s going to go through the clinical lab. So he has to order this several weeks in advance. The target area in the nuclear reactor has to be booked in advance for that material to be made, and it has to be done very carefully because of the short half-life of polonium. If there’s a long delay in this, that means the radioactivity will decay; it will become less and less effective.

So not only could it be produced only by a state enterprise, but it also requires a rather formal sort of way of making it. All those resources have to be put together in advance.

Could you trace this back to some country or to some particular reactor?

This material, polonium-210, is primarily an alpha emitter, but it has about 1 to 2 percent of beta gamma activity in it, usually from contaminants or pollutants. A little bit of decay activity produces beta gamma. So what you have is a spectral signature. That means you can tell when it was put in the reactor to be generated. The first thing you can get from decay, from its strength, is, you can trace back and say, “Ah, OK, this was in a reactor 15 days ago, or 28 days ago.”

It is possible to get a signature for the lab that separates [the polonium] from the other radioactive materials that are generated. If you have a signature for that particular lab, then you could identify it. Now, because this would have come from a military type of establishment, it’s unlikely that other countries would have a signature of that establishment.

Are the Russians in particular known for producing polonium?

Well, most countries that have an atomic weapons program are. It was a little device, or a trick, used to initiate the earlier series of atomic weapons. It has one or two other uses, but in very small quantities, very specialized. I believe it’s on the [Nuclear] Non-Proliferation [Treaty] embargo list.

Why would you use this to poison somebody?

I was very surprised, because it’s an alpha emitter, which is a heavy ionizer, but generally it’s a difficult one to use if you were to have it ingested in food or something like that. One of the things about human beings is that our gut is designed to protect us from being poisoned. So the gut lining doesn’t pass toxins into the blood. This would be seen as a metal, and if you look — health physicists have what they call gut-transfer factors, and the gut-transfer factor for polonium is quite low. Not a lot of it can get through.

The first challenge, if you’re going to administer this as a toxin via the mouth or by liquid — you’ve got to somehow cut it chemically with something to make it diffuse into the gut and out of the gut into the bloodstream so you can get it into key organs. The way in which you cause the collapse of this victim is to concentrate the radioactivity in a number of key organs: the kidneys, the liver, and in this case in the bone itself, on the bone surfaces. You then get a lack of red blood cells, and the whole system starts collapsing. Now, to do that as an ingested thing is quite difficult. You’d probably need some sophisticated chemical cut into it.

If you could get it into the respiratory tract, down into the depths of the lungs — and if the particles are small enough, less than, say, 5 millionths of a meter, 5 microns — then you can pass it through the lung tissue into the bloodstream, where it can do its evil work. Even then, and I haven’t done the sums on this, but I would guess to get a lethal dose, about 5 units of radiation, would take some months.

That’s what’s so strange about this. First of all, how was it administered? Was it administered through the ingestion pathway or the respiration pathway? The respiration pathway would require some quite sophisticated chemistry, and if it was [administered that way], it seems a bit too effective. So was there some trick, not only a chemical trick but a radiological trick, applied to this?

Almost 30 years ago in London, we had the Bulgarian dissident [Georgi] Markov, who was injected with a ceramic pellet from an umbrella. That was very advanced technology for its day, and I’m beginning to sense that this particular radionuclide might be part of a very advanced designer toxin. It may even involve nanotechnology. But it’s certainly caught everyone by surprise here; we were just ill-prepared for this.

Everybody’s focusing on the sushi Litvinenko ate, but you’re talking about the respiratory tract. Do you think it wasn’t in the sushi?

I think it was the respiratory tract. [And] I think if it was via the respiratory tract, it would take a lot longer than the sushi bar, so you’d look for somewhere he’d stayed, perhaps for several hours.

But who knows? The problem is, if it was a well-designed toxin, then it could have gone in anywhere. It could have been an injection.

This is absolutely unique. It’s an awkward thing to administer, because, as we’ve seen, it leaves a trail. If you administer this to anyone, it’s not only got a radiological half-life, but it’s also got a biological half-life. Put this stuff in the body, and an amount of it will come out in a number of days, and it will continue. Most obviously in the urine, but also in sweat. So your victim will leave a trail.

The initial reports were saying this shouldn’t have been detectable.

Oh, no, of course it would be detectable. First of all, the initial reports were wrong in that they assumed it was a pure alpha emitter. Well, it’s going to have some beta gamma, so that makes it readily detectible. Secondly, the symptoms he was displaying were that of radiation poisoning: loss of hair, low blood count, et cetera.

In Britain we have something similar to your Homeland Security system. We have something called Resilience. Last year we had an exercise for a radiation dirty bomb attack, and the police took over an area of London and displayed how wonderful they were, with all their different-colored spacesuits and chemical suits, and they had police cadets playing the injured, and of course everything went off absolutely smoothly, the disaster was averted and a nation was saved. Of course, [laughs] come, instead of a terrorist with a dirty bomb, one assassin with some polonium, and the whole system just collapses.

You’re saying this exposed problems in the British system. Where do you think the breakdown in the system was? Should they have been detecting the polonium coming into the country?

No, the breakdown was … as soon as he’s referred to University College Hospital, which is a frontline defense hospital, then they should have picked it up there.

In terms of knowing that the thing was in transit: These isotopes are very difficult to track externally. If it was a state-sponsored assembly, then it’s more likely the courier would have been very effective, so there wouldn’t have been any leaking during the courier stage, when they were transferring it from wherever it was to London, if he was in fact dosed in London. So therefore it means the tracking that’s going on at the moment is probably either a victim or somebody who’s contaminated by way of.

What they’re finding now, these traces of radioactivity on the planes, you can actually pick those traces up and bring a sample back to the lab?

Yeah, you can pick it up with a swipe; you can swab it, or you can tack it onto a tape. It’s not difficult. And then you run a spectral counter over it for, let’s say, 30 minutes to 100 minutes or however long it takes.

What I should say, by the way, is I’m not at all convinced by all this radiation being detected here, there and everywhere. You have to be very, very careful when you’re monitoring for radioactivity; you can jump the gun in many ways. Say, for example, that someone had been in hospital and had a radioactive bromide meal for an X-ray system. Well, for several days or weeks afterward, they’re going to be passing traces of that particular dose that they’ve had. It wouldn’t necessarily be polonium, but it would be a radioactive trace. So when you go to an aircraft and suddenly you find some radioactivity in the toilet, that may be completely disconnected. All of these contaminants have to be isolated from inside the aircraft to make sure you’re just looking at polonium.

So do you think — and this is the reason I’m asking about the detectability issues — someone’s trying to send a message here?

Well, who knows? I’m a technician, but I would guess yes, because it’s a pretty awful death, as we’ve seen.

Is it possible, then, that they may have made a mistake and given him more than they’d intended and made it more easily detected?

This is a very publicized death: a painful, prolonged and demeaning death. And it could be a marker being set down for other dissidents. That’s if I was to assume that it was a state doing it.

I think the problem we should be concerned with is, OK, here’s one that’s come up in the U.K., which is a sophisticated, technological country. What happens if someone is in Mexico or Chile? I don’t want to be rude to those countries, but what if there was a dissident in — I don’t know — the Congo. What would happen to somebody targeted like this in a country that hadn’t got a nuclear background?

It’s very odd, isn’t it? Because whoever did this must have known that as soon Litvinenko died, the system would have been onto it like a pack of hounds. The problem is: Did he die too early? Or was he given too high a dose? Something’s gone wrong with this, hasn’t it? All that trouble to manufacture this toxin, to make a designer thing, to get it into him.

They must have known that as soon as he died in these circumstances, unless they had the time for the trail to go cold, then they were in trouble. I wonder if they were too effective. We’ll never know, will we? At this stage, all the indications are that this is becoming politically very, very sensitive, so one assumes that the shutters will come down, and no more meaningful information will come out.

This story has been corrected since it was originally published.

After three and a half years — and almost 3,500 posts and stories — today is my last day at Salon, and this is my last post. It’s time for me to move on, to get back to the longer-form writing I did when I first started at Salon and have missed ever since taking the reins of War Room from Tim Grieve a little more than two years ago.

When I was in college, Salon was a dream job, one I never thought I’d get. It didn’t let me down; working here has been a fantastic experience. I’d thank everyone who’s helped me over the years individually, but we’d be here all day, because there are just so many great people at Salon. So instead, let me just thank everyone I’ve worked with — though, really, mere thanks are inadequate for everything they’ve done for me.

There’s been quite a bit of turmoil and bad news over at the Republican National Committee lately, and Monday evening brought more: One of the RNC’s top officials, Chief of Staff Ken McKay, has resigned.

The resignation is effective immediately, the RNC announced. Mike Leavitt, who worked on Sen. John McCain’s 2008 presidential campaign and has been the party’s deputy chief of staff, will be replacing him.

This move comes in the wake of revelations that the RNC allowed a staffer to expense the cost of taking potential donors to a Los Angeles nightclub that often features topless women, with a bondage theme. That news had only sharpened the criticism Steele has faced over the organization’s spending during his tenure, and increased the pressure on him to do something about it. It appears this resignation is both an attempt to show something is being done and to throw McKay under the proverbial bus.

For years now, it’s seemed like the word “maverick” was permanently fused to Sen. John McCain, R-Ariz. He seemed to cherish it, and his advisors often worked to push it; they may have played it down a little during the 2008 Republican presidential primary, but it was an essential part of the eventual nominee’s image during the campaign.

Now, though, McCain is in another Republican primary, facing a legitimate challenger from his right — former Rep. J.D. Hayworth — in a decidedly anti-incumbent year. So he’s been reinventing himself to some extent. He went to the right on immigration, for instance, despite the fact that his moderation on the issue had been one of his signatures between the 2000 and 2008 campaigns.

The senator’s latest step in that direction goes much further than that, however.

“‘Maverick’ is a mantle McCain no longer claims; in fact, he now denies he ever was one,” Newsweek’s David Margolick reports in a new article, quoting McCain as saying, “I never considered myself a maverick.”

Following up on Gabriel Winant’s earlier post on conservatives’ feelings about this year’s Census, here’s an interesting bit of news: The Census Bureau has tapped Karl Rove for a new public service announcement in which he encourages people to return their forms.

Conservatives farther out on the fringe might be wary of the Census, but Rove is smart enough — and mainstream enough — to know that it could be politically disastrous for the Republican Party if the right has an unusually low response rate. That might be what’s motivating him here.

The Birthers are back.

They never really went away, actually — in all likelihood, unfortunately, they never will — but the people who believe President Obama doesn’t meet the Constitution’s eligibility requirements for his office have at least faded from the news lately. Now, some are working to change that, and they have a new figurehead to rally behind.

Last week, the American Patriot Foundation announced that Army Lt. Col Terrence Lakin, a flight surgeon, has decided that he’ll refuse to obey any and all orders because of his concerns over the circumstances of Obama’s birth and birth certificate.