'MISSING PIECES'

Suspicion had originally fallen on Curtis because of wording contained in all three ricin letters, which included his initials "KC."

Dutschke has told local media that he knew Curtis but had only had contact with him three times, and not since 2010.

Curtis, 45, told the Northeastern Mississippi Daily Journal that he believed Dutschke deliberately sabotaged his career as a performer by calling sponsors and telling them about Curtis' numerous prior arrests. "I lost 12 really big shows in 2011 and eight in 2012 directly linked to him," Curtis told the newspaper.

Dutschke, who fronted a two-man blues band in Tupelo called RoboDrum, ran unsuccessfully as a Republican candidate in 2007 against Stephen Holland, a Democratic state representative from the Tupelo area. Holland's mother, Sadie, is the judge to whom one of the ricin-tainted letters was mailed this month.

Curtis's brother and fellow Elvis impersonator, insurance agent Jack Curtis, worked for a time with Dutschke and said he believed the feud with Dutschke was related to his brother's efforts to publicize allegations about a black market for body parts at a local Mississippi hospital.

Kevin Curtis was fired as a janitor from North Mississippi Medical Center in Tupelo after raising questions about body parts he said he observed there. The hospital strongly denied the allegations.

Dutschke faces other charges related to an April 1 indictment for fondling three children between ages 7 and 16, from 2007 to 2013, according to court records.

RICIN POTENCY

The FBI said on Thursday that more tests may be necessary to determine the potency of a granular material identified as ricin contained in the letters.

An FBI agent testified in court in Mississippi that the ricin found in the letters was in a crude form and looked like castor beans ground up in a blender, according to media accounts. Experts have said ricin in that form would have a low potency.

Castor bean plants are grown as ornamental shrubs in the Southern United States, but there is no domestic castor oil production and it is mostly imported from India and China.

Milton Leitenberg, senior research scholar at the Center for Strategic and International Studies at the University of Maryland, said the vast majority of ricin cases since the 1960s had involved crude ricin preparations made from recipes published in manuals and on the Internet.

"You could ingest this crude stuff, swallow a couple of tablespoons and you'd probably vomit, but not much more," Leitenberg said in a telephone interview.

A material like that described in the ricin court hearing would pose little danger, Leitenberg said.