A federal magistrate judge in Bangor denied bail Monday for a Windham man accused of mailing a poisonous chemical to a suicidal man in the United Kingdom who used it to kill himself.

Sidney P. Kilmartin, 52, has been held in federal custody since his arrest Nov. 5 on charges that he sent potassium cyanide to a man identified in court records as Andrew Denton of Kingston-upon-Hull, England, who died in December 2012.

U.S. Magistrate Judge John Nivison denied Kilmartin’s request to be released while the case is pending against him, after hearing arguments from lawyers Monday afternoon in U.S. District Court in Bangor.

Kilmartin knew that Denton intended to use the potassium cyanide to kill himself, according to a summary of the investigation released Thursday by Humberside police in England.

Kilmartin and Denton exchanged emails in which Kilmartin offered to sell Denton cyanide and gave him advice on how to use it, the police in England said in the written statement last month.

Kilmartin pleaded not guilty at his initial court appearance in Bangor the day he was arrested on charges of mailing injurious articles and mailing injurious articles resulting in death. The two charges stem from two batches of cyanide that he is accused of mailing on Nov. 16 and Dec. 11, 2012, according to the indictment against him.

While federal law requires that a person arrested be allowed a detention hearing within days of his arrest, Kilmartin voluntarily delayed his bail hearing to allow new lawyers assigned to his case to prepare arguments and set schedules, according to court records.

The first batch of cyanide that Kilmartin sent in 2012 failed to kill Denton, and Denton complained about its quality. Kilmartin then allegedly mailed him another batch. Denton, 49, was found dead on Dec. 31, 2012, with 17 milligrams of cyanide per liter in his blood – more than three times the lethal dose of 5 milligrams per liter, according to Humberside police.

While the British authorities provided more details about the case than federal authorities in Maine, who arrested Kilmartin at a gym in Windham on Nov. 5, no one on either side of the Atlantic is saying how Kilmartin was able to obtain the poisonous chemical or how he and Denton found each other despite living nearly 3,100 miles apart.

It’s not known whether Kilmartin sent cyanide to anyone else.

Authorities allege Kilmartin was able to obtain cyanide – and deal it internationally – despite a history of mental illness and drug addiction.

He had been involuntarily committed to Riverview Psychiatric Center in Augusta until less than a year and a half before he is accused of mailing the first batch of cyanide overseas on Nov. 16, 2012. He is accused of mailing the fatal dose on Dec. 11, 2012, while living in an independent apartment with psychiatric supervision, according to state and federal court records.

Potassium cyanide is a highly toxic colorless salt, similar in appearance to sugar, according to the U.S. Centers for Disease Control and Prevention. Used commercially for fumigation, electroplating and extracting gold and silver from ores, it is usually shipped as capsules, tablets or pellets. It releases highly toxic hydrogen cyanide gas, which interferes with the body’s ability to use oxygen. Swallowing the chemical causes nausea, vomiting, abdominal pain and irritation or corrosion of the lining of the esophagus and stomach. Ingestion can quickly become fatal.