Sidney Kilmartin advertised and mailed a substance he said was cyanide to several suicidal people, investigators said. The substance was really Epsom salt. But authorities said he later sent the real thing to Andrew Denton, who used it to kill himself. Investigators said he wanted to prevent Denton, who lived in Hull, from going to authorities about his fraud.

Kilmartin, who used to live in Windham, was convicted on Tuesday of mailing injurious articles resulting in death and witness tampering. He had denied those charges but earlier had pleaded guilty to mail fraud and wire fraud. He was found not guilty of witness retaliation.

Sentencing has not been scheduled, said federal prosecutor Halsey Frank, who declined to comment on the case until after Kilmartin is sentenced. Kilmartin faces the possibility of life in prison.

Jurors deliberated for about 2 1/2 hours following the trial, which began on Oct. 3.

Kilmartin’s attorney tried to make the case that prosecutors did not successfully prove that Kilmartin was responsible for Denton’s death. The attorney, Martin Ridge, conceded that Kilmartin was guilty of defrauding Denton.

Ridge didn’t immediately respond to a request for comment after the verdict.

An affidavit by a U.S. postal inspector said Kilmartin obtained the cyanide by posing as a jeweler to persuade a California distributor to ship him 100 grams of the chemical for $127.56.

Potassium cyanide is a highly toxic salt that looks like sugar. Swallowing it causes nausea and vomiting and can kill a person quickly.