(Editor's note: Dr. Raghavakaimal was later acquitted of all charges.)

A research scientist and associate professor of medicine at the Mayo Clinic in Rochester is under investigation by the FBI for purchasing potassium cyanide for use as "a chemical weapon" in
connection with a domestic dispute, according to a federal search warrant unsealed this week in St. Paul.

According to a sworn affidavit filed by the FBI, the matter came to light when Rochester police arrested Sreekumar Raghavakaimal, 46, on domestic assault charges Feb. 4.

He was charged the next day in Olmsted County with felony terroristic threats, felony false imprisonment, gross misdemeanor interference with a 911 emergency call, and misdemeanor domestic assault, according to Julie Germann, the prosecutor in the case.

According to the FBI affidavit, here's what prompted the charges: Raghavakaimal's estranged wife said they had argued over a ring he wanted returned, and he got a knife from the kitchen and bolted the door when she tried to leave.

She said that he broke her cell phone in two when she tried to call 911, and that he threatened to cut the throat of their 11-year-old son if she screamed for help.

Raghavakaimal wanted to get back together, and made comments that led his wife and son to believe he was suicidal, the affidavit says. When she managed to leave, she took a vial with her that she believed contained pain pills. When police investigated her complaint that day, Raghavakaimal told them he was not suicidal, the FBI said.

But he offered that he did buy some potassium cyanide on the Internet after he and his wife had separated in December 2005.

Tests on the vial taken by Raghavakaimal's wife show that it contained nearly pure olive oil. According to an FBI expert cited in the search warrant affidavit, "The combination of olive oil and
cyanide is specifically mentioned in The Mujahideen Poisons Handbook (authored by Abdel-Aziz)" as a way to increase the toxicity of cyanide when applied to the skin.

The FBI says it discovered that Raghavakaimal had actually ordered the potassium cyanide through the Mayo Clinic, although it was not used at the labs he supervised there.

Raghavakaimal could not be reached for comment Thursday or Friday. He has a doctorate in chemistry and was the Director of Human Genomics and Proteomics Core at the Mayo Clinic College of Medicine's General Clinical Research Center before it was reorganized, said Adam Brase, a spokesman for the Clinic.

Brase said Raghavakaimal's main appointment is as a research scientist in endocrinology, and he also carries a title of director of the Microarray Core Facility.

Brase declined to comment further on Raghavakaimal's employment status. He said the Mayo Clinic would cooperate in the investigation.

The FBI obtained a search warrant for Raghavakaimal's house on Feb. 14, saying there was probable cause that other toxic chemicals would be found there. Agents seized a variety of computer equipment, documents, two point-and-shoot cameras and three rolls of film, records show.