In the last five years, three Rikers Island inmates have died after apparent beatings from guards at the prison facility. To date, none of the guards involved in those beatings has been charged with a crime, the Associated Press reports.

Angel Ramirez, who died in 2011, was hallucinating from heroin withdrawal and alcohol when he attempted to punch a guard and missed. Earlier in the day, he complained to staff about "seeing people throwing knives at him and trains going around his bed." After Ramirez took his swing, a guard pulled him beyond the view of security cameras, and three more joined in beating him, according to investigative documents. Fellow inmates, the AP reports, "told investigators they heard screaming and the sickening crack of nightsticks against bone."

Ramirez died of blunt-force injuries including shattered ribs and a stomach full of blood. The guards involved weren't prosecuted, and the Ramirez family is now suing the city.

A spokesman for the Bronx District Attorney's office told the AP prosecutors didn't believe they could prove criminality in Ramirez's death, which was ruled a homicide by the medical examiner's office. There are several reasons why that might be the case:

Criminal cases against correction officers are notoriously rare and difficult to prosecute. That's because attorneys representing jail guards expertly challenge the credibility of inmate witnesses, a code of silence permeates the ranks of officers, and inconsistencies in video footage and statements are easily exploited by defense lawyers, experts say.

Clarence Mobley, 60, was fatally beaten by guards after hitting one in the face with a food tray in 2009, and Ronald Spear, 52, died this year after a guard kicked him in the face. According to the AP, Spear previously claimed guards "retaliated against" him because he complained of having difficulty getting treatment for his kidney disease.

[Image via AP, h/t ANIMAL]