With the reports that Chicago police run a not-so-secret “black site” for illegal, abusive detentions and Louisiana officers conspired to frame a law-abiding process server for battery of a policeman, law enforcement practices are again in the news for colluding against members of the public.

Many instances of police violence may genuinely be perpetrated by just a few unrepresentative officers. But often, other officers witness inappropriate violence or recognize would-be “problem officers” but are unable or unable to do or say anything about it.

Why would people who dedicate their lives to fighting injustice tolerate it among themselves?

The code of silence, also known as the “Blue Wall of Silence,” is an unofficial method of discipline that operates among police officers all over the country. Violation of the code may result in quasi-official sanction such as being passed-over for promotion. It can also lead to harassment, such as toy rats or even dead rats being placed in the violator’s police locker, or worse.

Fear of retribution for violating the informal but pervasive code not only applies to personal indiscretions, but allegations of serious wrongdoing, including violence. Possible retribution can be severe, such as termination or mass refusal to come for back-up in a dangerous situation.

In his book, Police Corruption: Exploring Police Deviance and Crime, author Maurice Punch explains that police culture, like military culture, is tight-knit and typically demands a deep level of trust among its members. This is due to the sometimes extraordinary dangers associated with the job. A rookie officer often must demonstrate his loyalty to his comrades, either through some hazing ritual or another unofficial test. This test may be minor rule-breaking, such as accepting free food or drinks on duty, or may involve actual law breaking, such as skimming cash from a drug suspect. Thus, from jump, some officers are initiated into a police culture which maintains, from day one, the loyalty-above-all method of operation.

The late professor and Broken Windows policing progenitor James Q. Wilson, in his book Bureaucracy, explained how a rookie officer is greeted by veterans on his first day on the streets: “Forget what you learned in the Academy. I’ll show you what police work is really all about.” Much like official training for any structured or corporate job, there are the ways things are supposed to be done, and the ways things actually are done.

Taken together—a brotherhood based on loyalty that is governed by informal practice and internal, secretive discipline—it’s hard to square this with each officer’s oath to his constitutional duties. Put another way, when loyalty to one another trumps dedication to justice and individual rights in the minds of officers, abuse will not only happen, it will be tolerated and thus implicitly encouraged.

To be sure, such systems do not turn everyone into “bad cops.” There’s no inherent contradiction in believing that most officers are trying to do the right thing while also recognizing that the way many departments operate is less-than-ideal. Systemic problems like the Blue Wall have been entrenched in many police departments for quite some time.

After a spate of corruption in New York City in the early 1990s, Judge Milton Mollen headed a commission (Mollen Commission) to investigate the causes of the corruption within the NYPD. The Mollen Commission described the widespread perversion of justice well in its summary of its investigation:

“What we found is that the problem of police corruption extends far beyond the corrupt cop. It is a multi-faceted problem that has flourished in parts of our City not only because of opportunity and greed, but because of a police culture that exalts loyalty over integrity; because of the silence of honest officers who fear the consequences of “ratting” on another cop no matter how grave the crime: because of willfully blind supervisors who fear the consequences of a corruption scandal more than corruption itself; because of the demise of the principle of accountability that makes all commanders responsible for fighting corruption in their commands; because of the hostility and alienation between the community in certain respects which breeds an “Us versus Them” mentality; and because for years the New York City Police Department abandoned its responsibility to insure the integrity of its members.”

Police officers will make honest mistakes and civilians may be hurt, as a result. If an officer acted reasonably but ultimately incorrectly, his fellow officers who could mentally place themselves in his situation would naturally sympathize with him. Add to this the antagonism that naturally develops between police and suspects, the “Us versus Them” dynamic the commission noted would likely reify this divide and incentivize the police to protect their own.

That said, the Mollen Commission found that many officers resented “bad cops,” but felt powerless to do anything about it for fear of retribution. It is safe to say that the reflexive institutional urge to protect police officers who make mistakes has the unintended consequence of insulating “bad cops” from the consequences of their actions. But those fears of retribution were not unfounded then, nor are they two decades later.

In 2010, the Village Voice published an exposé of New York City police officers in Bedford-Stuyvesant’s 81st Precinct. The report was based on secret tape recordings by an officer in the department that revealed police practices that had been denied publicly, including arrest quotas and manipulation of criminal charges to satisfy departmental statistical goals.

The whistleblower, Officer Adrian Schoolcraft, was dragged from his apartment by police supervisors, and involuntarily committed to a mental health facility for six days—on those supervisors’ claims of instability. (Claims proved to be false by yet another Schoolcraft secret recording.) After his release, he was harassed at his home by officers on numerous occasions.

Nearly five years later, Schoolcraft, having left the force, is awaiting action on the $50 million lawsuit against the city, hospital, and department for retaliation and false imprisonment. Despite the depth and detail of the Voice’s reporting, the NYPD didn’t publicly confirm the tapes’ veracity until a report released in March 2012.

The plight of Officer Schoolcraft and other whistleblowing officers—who have been harassed and punished for telling the truth—is, as Radley Balko put it, the most successful “Stop Snitchin’ ” campaign in the country. I can imagine few scenarios more intimidating than a large number of armed individuals who view you as disloyal, and to whom disloyalty is the singular unforgivable sin.

The problems of secrecy are not limited to the vigilante justice meted out by officers. The secrecy of officer discipline is baked into the laws and rules of police departments all over the country. Laws and policies I mentioned in my last essay also enhance the secrecy of police discipline.

In some jurisdictions, the police departments are prohibited from, or free to refrain from, releasing names or offenses of officers that are suspended pending administrative investigations. Of course, if an officer is arrested, the information automatically becomes public information. However, if the investigations are handled in-house, acts that would appear to be criminal to the public may be dealt with by administrative reprimands with no outside accountability or oversight. An officer that continues to be cited for use-of-force excesses but is never charged with a crime may stay on the force indefinitely, anonymous to everyone but those whom he victimizes.

A somewhat recent case in point was in Springfield, Virginia. John Geer was a distraught and intoxicated man shot and killed by a Fairfax County police officer in August 2013. Repeated pleas by the media went ignored until documents were finally released in late January 2015. The reports show that four other law enforcement personnel at the scene of the shooting contradicted the statements of the shooting officer. Specifically, three officers and a lieutenant stated that Mr. Geer had his hands up, and thus posed no imminent danger to the officer who shot him. The shooting officer, on the other hand, insisted his hands dropped and that the shooting was not accidental.

The U.S. Department of Justice’s Civil Rights Division is investigating the incident, but there’s been no explanation why it took 17 months for the police to release their version(s) of what happened. Neither has the officer’s current employment status—whether he is on active duty or not—been reported, nor why evidence has not been presented to a grand jury for possible criminal indictment. The Washington Post opined, “Fairfax’s County’s governing body, the Board of Supervisors, seems incapable of getting its own employees — namely the police and the County Attorney’s office — to conduct themselves responsibly and transparently.”

In many jurisdictions, there is no effective and reliable mechanism to combat the secrecy and loyalty engendered in their police agencies. So long as officers are left to be responsible for their own discipline, continue to distrust outsiders who may punish them for honest mistakes, and maintain professional cultures that conflict with their sworn duty to abide by the Constitution, an intolerable amount of police violence will continue to go unpunished.