Bronx District Attorney Darcel Clark announced on Friday that it was an "absolute tragedy" that Polanco died from an epileptic seizure, but after a thorough investigation there was "no criminality."
Polanco, 27, was arrested on April 16, 2019, for alleged possession of a controlled substance and assault of a cab driver, court records show.
She was being held on $500 bail at the jail’s Rose M. Singer Center, a female unit that houses transgender women.
Rikers Island is one of the world's largest correctional institutions and has become the target of activists calling to shut it down. The city council approved a measure last year to shut the prison down, a decision supported by New York City Mayor Bill de Blasio, however, it won't be shut down until 2026, according to the plan.
On June 7, 2019, Polanco was found dead in her cell where she was being held in solitary confinement. An autopsy report from August 2019 found that the manner of death was natural and that the cause of death was "sudden unexpected death in epilepsy (SUDEP) due to a mutation in the CACNA1H gene."
"Her family and friends along with the public deserved to know whether anything else played a role in her death. It is an absolute tragedy that Ms. Polanco died so young," Clark said in a statement after announcing the investigation's finding.
Included in the six-month investigation were thousands of pages of medical and corrections records as well as interviews with correction officers, medical staff and other inmates.
While the investigation did not find criminal wrongdoing, it found that Polanco was not checked on by a suicide prevention agent for 47 minutes, prosecutors said. Corrections officers are supposed to check on inmates every 15 minutes, according to DOC policy.
"At a minimum, every inmate housed in Punitive Segregation shall be observed at least once every 15 minutes at irregular intervals," Margaret Garnett, the commissioner of the Department of Investigation, said Friday.
The DOI referred the investigation to the Department of Correction to take "any action it deemed appropriate" against its employees.