You could not, not even with the aid of many, many Hollywood writers, concoct this story if you tried.

Last Friday, as if on cue from some kind of unscrupulous Los Angeles studio head, just days after the sixth episode of FX’s The People v O.J. Simpson: American Crime Story aired, a celebrity news website broke the kind of news that lives on the front pages of major papers and news websites. A knife that may have been discovered buried on O.J. Simpson’s former property nearly two decades ago and kept by a Los Angeles police officer, who is now retired, came into police custody for testing only sometime last month.

Whether the events and information prove to be either definitive or a rather distasteful joke, the United States can and probably will busy itself again with the salacious details of the victims’ lives, their brutal deaths and the man whom millions of Americans believe got away with two murders. The verdict by the mostly black jury in Simpson’s 1995 double-murder trial for more than two decades has been widely lampooned and criticised. Simpson’s blood, after all, was found at the crime scene. But the jury’s refusal to convict him probably should have been understood as a national warning, one that is particularly relevant today.

When the unlawful and sometimes deadly actions of some police officers go unobserved, unexamined and unpunished, it’s not just the lives of Americans of colour — those disproportionately likely to suffer various forms of police and justice system abuse — that are devalued and rendered less secure. The entire concept of justice is eroded and the process we use to try to render it prone to folly. The connection between the kind of alleged brutality that made the Los Angeles Police Department infamous in the 1990s and a mostly black LA jury’s refusal to convict Simpson is real. It was the primary reason that large shares of black Americans and white Americans did not view the verdict the same way back then. (Only in 2015 did a majority among both say Simpson was guilty.) And that connection ranks among the primary reasons that more widespread allegations of police misconduct should be taken seriously today.

Oddly, or perhaps ironically, the events and information relayed on Friday did not give present-day America its first chance to grasp the connection between lawful policing and the ability to lawfully and successfully prosecute those who may have committed deadly crimes. At least some bit of that credit has to go to the producers and writers of the much-watched, more-campy-than-probative aforementioned miniseries, The People v O.J. Simpson (FX made the first six episodes of the miniseries available to some reporters for advance viewing.)

Yes, the miniseries includes multiple scenes dedicated to conveying the faith and fame-is-fleeting values that late Simpson attorney Robert Kardashian tried to impart to the pre-reality TV Kardashian clan. Yes, the writers have made a particularly cynical, silver-tongued villain of the late Johnnie Cochran, the lawyer who led Simpson’s legal team. Cochran is not alive to explain his choices.

Yes, producers and writers displayed all the critical thinking skills required to depict the all-white trio of Time magazine staff who put a darkened image of Simpson on its cover as a group clueless and, therefore, apparently innocent of adding to the lineage of racist, fearmongering imagery. (This all-white group of image specialists was simply hungry to create an indelible cover, according to the miniseries.) And, yes, the people responsible for The People v O.J. Simpson dubbed an entire episode “The Race Card”. It is as if the minds behind the programme continue to believe that race is something that an individual can opt to tuck away or to deploy at will, rather than an omnipresent force shaping every American’s life.

Well, in fairness on that last point, lots of people believe that same fiction. Before his arrest and trial, Simpson was, according to the programme, one of them.

But the minds behind The People v O.J. Simpson did, at least, have the wisdom to begin the series with some essential bits of context. The miniseries starts with footage of the LAPD’s 1991 beating of Rodney King. That footage is followed immediately by images culled from news of the 1992 Los Angeles riots. Those riots, of course, erupted after yet another jury — this one mostly white — decided to acquit three of the officers involved in King’s beating of state criminal charges. Viewers need to know and see both bits of footage to grasp the Simpson jury’s ultimate decision.

A mostly black jury seated in LA would have been aware of the King beating, the riots and the damning contents of a 1991 outside inquiry into the LAPD, which found that excessive force was not simply common; many of the nearly 1,800 officers involved in the four years’ worth of incidents that the commission examined had received promotions and positive reviews. One officer had 16 excessive-force or other complaints and was still employed. When you digest that, it is not at all hard to understand why the mostly black panel did not trust or believe what is often described as copious physical evidence against Simpson.

Of course, among the many differences between 1995 and 2016 is this: what the mostly black jury in the Simpson trial knew about the LAPD and its practices via the headlines, as well as their personal experiences and those of their family and friends, is today knowledge that much of America can have, if it so chooses. Today, there is a seemingly constant flow of mobile phone and dash-cam videos of police officers beating, shooting, killing or maiming private citizens.

Now, turn your attention back to the events of Friday, keeping in mind the King beating, the officer acquittals, Simpson’s not guilty verdict and more recent cases involving unarmed, homeless and mentally ill people fatally shot by the LAPD. The national lesson that should have been taught by the Simpson verdict is far clearer. So, too, is the disturbingly familiar, credibility-damaging behaviour of the LAPD.

On Friday, LAPD spokesman Captain Andrew Neiman stepped out on to a sunny LA sidewalk and explained that the knife allegedly discovered on Simpson’s property has been sent to a police lab for testing. The lead investigator in the Simpson case, detective Tom Lange, now retired, gave a telephone interview to CNN playing down the significance of the knife. As Lange put it, others have been found in the area before.

The two men might as well have said: “America, you can trust us. We’re the LAPD.”

The agency may have a reputation, verified track record and continuing problems connected to alleged illegal and unethical policing. Yes, highlighting some of those facts formed the basis of Simpson’s successful, if beyond opportunistic, defence.

Sure, one of the LAPD’s own retired officers may have thought it just fine to keep a knife possibly associated with a double-murder case that is still open. The knife may be in police custody now only because that same retired officer had plans to mount and display his twisted treasure. And, yes, the man whom millions of Americans believe committed the crime cannot be tried again no matter what the testing finds.

But America can trust and believe that the LAPD will adequately test the found knife, then ethically and honestly report its findings. Right.

An ethical and effective police department in a democratic society should and must be able to withstand scrutiny. It is the linchpin of real public safety.

• Janell Ross is a reporter for The Fix and a contributor to The Washington Post, who writes about race, gender, immigration and inequality