Holbrook Mohr

JACKSON, MISS.: The key ingredient — castor beans — is easy to find. Crude instructions for extracting the lethal poison in them can be found on the Internet. And it doesn’t require a chemistry degree or sophisticated lab equipment.

The FBI is investigating at least three cases over the past month and a half in which ricin was mailed to President Barack Obama and other public figures.

Ricin has been sent to officials sporadically over the years, but experts say that there seems to be a recent uptick and that copycat attacks — made possible by the relative ease of extracting the poison — may be the reason.

“I can absolutely promise you that when these kinds of things happen, we’re going to have copycats. We expect them. We prepare for them. And we catch them,” said Murray Cohen, founder of the Atlanta-based Frontline Foundation, which trains workers in how to respond to bioterrorism and epidemics.

Security and counterterrorism expert Michael Fagel, who teaches at Northwestern University and is a veteran of ricin investigations, said ricin may be employed because castor beans are so easy to come by.

The plants grow wild along highways and in other spots in the U.S.

“And you can go on the Internet and find out any one of a gazillion recipes on how to make ricin,” Fagel said.

If inhaled, ricin can cause respiratory failure, among other symptoms. If swallowed, it can shut down the liver and other organs, resulting in death. The amount of ricin that can fit on the head of a pin is said to be enough to kill an adult if properly prepared. No antidote exists, though researchers are trying to develop one.

Despite the poison’s fearsome reputation, a draft of a 2010 Homeland Security Department handbook lists only one person killed by ricin, and that was a 1978 assassination in London involving injection with a ricin pellet.

The first of the three recent ricin investigations in the U.S. began in April. Kevin Curtis was jailed and accused of sending poisoned letters to Obama, a U.S. senator and a Mississippi judge. Then Curtis was suddenly released from jail when the FBI shifted its focus to his longtime foe, James Everett Dutschke. He was charged with making ricin.

Then in May, three poison-tainted letters were mailed from Spokane, Wash., to Obama, a federal judge and a post office. A fourth letter sent to Fairchild Air Force Base near Spokane was analyzed and tested positive for ricin. The FBI is also trying to locate a fifth letter it suspects was mailed to the CIA in McLean, Va.

In the most recent case, authorities say ricin-laced letters were sent to New York Mayor Michael Bloomberg and his Washington gun control group.