Cyanide can get into the body by being inhaled, swallowed or injected. Deborah Blum, an expert on poisons who has written about the detectives who pioneered forensic toxicology, said the use of cyanide in killings has become rare in part because it is difficult to obtain and normally easy to detect, often leaving blue splotches on a victim's skin.
"The thing about it is that it's not one of those poisons that's tasteless," Blum said. "It has a really strong, bitter taste, so you would know you had swallowed something bad if you had swallowed cyanide. But if you had a high enough dose it wouldn't matter, because ... a good lethal does will take you out in less than five minutes."
Only a small amount of fine, white cyanide powder can be deadly, she said, as it disrupts the ability of cells to transport oxygen around the body, causing a convulsive, violent death.
"It essentially kills you in this explosion of cell death," she said. "You feel like you're suffocating."
A relative came forward days after the initial cause of death was released and asked authorities to look into the case further, Cina said. He refused to identify the relative.
"She (the morgue worker) then reopened the case and did more expansive toxicology, including all the major drugs of use, all the common prescription drugs and also included I believe strychnine and cyanide in there just in case something came up," Cina said. "And in fact cyanide came up in this case."
The full results came back in November. Chicago Police Department spokeswoman Melissa Stratton confirmed the department was now investigating the death and said detectives were working closely with the Medical Examiner's Office.
Investigators will likely exhume the body, Cina said.
Calls to Khan's family went unanswered Monday. A knock on the door at the family's small, two-story house late Monday afternoon wasn't answered.