Juries almost always give police the benefit of the doubt when it comes to allegations of misconduct or killing a suspect, according to criminologists and psychologists who study the justice system. That may, in part, explain the decisions made by grand juries in both Staten Island, N.Y., and Ferguson, Mo., to not indict white police officers in the killings of black suspects.
"If it's related to their official duties in handling a street encounter that went bad, juries don't want to deny the officer the benefit of the doubt and are unlikely to convict," said Philip Stinson, professor of criminal justice at Bowling Green State University who researches cases of police misconduct across the United States. "Policing is violent and everybody recognizes it."
Stinson is principal investigator for a project by the National Institute of Justice entitled "Police Integrity Lost: A Study of Law Enforcement Officers Arrested" that looked at various crimes committed by police officers. The data does not include conviction rates, but Stinson says that incidents committed during work hours (as opposed to ones committed off-duty) nearly always favor the officer.
In contrast, police arrested for crimes using their own weapon are convicted 98 percent of the time, Stinson said.
Jurors also bring strongly-held beliefs to the courtroom, even when presented with evidence that may contradict those beliefs. A recent study by researchers at the John Jay College of Criminal Justice found that pre-trial publicity strongly influenced the decisions of mock jurors in assessing the guilt or innocence of police officers accused of killing an unarmed man.
The study used mock jurors who deliberated the case of several New York police officers who were charged with homicide in the case of Sean Bell, who was killed outside a Queens nightclub by more than 50 rounds.
"You might think evidence would affect their decisions, but at the end of the day, those effects (of pre-trial publicity) were still there," said Steven Penrod, professor of psychology at John Jay.
In fact, recent opinion polls of Staten Island residents taken before the verdict showed only 41 percent of the people questioned favored the indictment of the officer accused of choking Eric Garner to death. In New York City overall, that figure rose to 64 percent.
In the Garner case, the grand jury didn't get to hear from expert witnesses who may have disputed the officers testimony that he did not use a chokehold, which is forbidden by New York City Police Department policy.
"The grand jurors can ask questions, but there are no lawyers to cross examine," said Geoff Alpert, professor of criminal justice at the University of South Carolina and an expert in police misconduct. "It's always in favor of the prosecution."
While grand jury testimony is kept secret, the judge Thursday released some information about what kind of evidence the jurors reviewed: 50 witnesses, 60 exhibits, four videos and related photos. Bowling Green's Stinson says that most academic studies on juries have focused on trial jurors, not the secret deliberations of a grand jury.