Warning: The following contains SPOILERS for Only Murders In the Building episode 6, "To Protect and Serve."
Despite being largely comedic in tone, Only Murders In the Building acknowledged one thing that more serious true-crime series do not; it is rarely easy for police detectives to reopen a case once it has been closed. This is ironic given how many other nominally realistic mystery shows make it seem incredibly easy for independent detectives to crack a case by uncovering a single clue, usually making the police look incompetent in the process.
The plot of the critically acclaimed and positively reviewed Only Murders in the Building centered around the death of financial advisor Tim Cono (Julian Cihi). While the police were quick to dismiss Cono's death as a suicide, three of his neighbors were not convinced, based on a phone conversation they overheard on the elevator just before Kono's death. This led Charles-Haden Savage (Steve Martin), Oliver Putnam (Martin Short), and Mabel Mora (Selena Gomez) to join forces in investigating Cono's death and producing a podcast based on what they uncovered. Hilarity ensued as the amateur detectives stumbled across evidence of a sinister conspiracy while pursuing improbable theories, such as Oliver's belief that legendary singer Sting was the killer.
Only Murders in the Building episode 6 opened with an unexpected shift, as the narration duties were taken over by Detective Williams (Da’Vine Joy Randolph), who hadn't appeared in the series since the first episode. A no-nonsense cop, Detective Williams was quick to complain about crime podcast listeners and "true crime nuts" making her job more difficult and dismissed the trio when they approached her about the possibility that Kono had been murdered. Detective Williams was similarly skeptical in "To Protect and Serve," when her wife mentioned having listened to the Only Murders In The Building podcast and asked about one of the random details the trio had uncovered that suggested someone was trying to cover up Tim Kono's murder. Annoyed at having her own wife questioning her competence, Detective Williams went back to work to look over the case files one more time, leading to the shocking discovery that someone in her department had prevented Kono's corpse from undergoing a toxicology analysis and that the NYPD internet technology team never looked over Kono's phone.
This left Detective Williams with a major problem and raised a point regarding real-world policework that most wouldn't expect a satirical series like Only Murders In the Building, with its cast of comedic actors, to address. The bureaucracy of the police department in a large city is immense and most homicide detectives work multiple cases simultaneously. This makes it difficult, even under optimal circumstances, for a detective to reopen a case once it has been closed, no matter how compelling any new evidence might be.
In the real world, homicide detectives are pushed to solve cases quickly and cleanly. The same is true in the world of Only Murders In the Building, and when Detective Williams' wife encouraged her to "swoop in there and reopen the case like a goddamn hero boss," she explained that she "can't get up to sergeant by opening a case that I already closed." This is why Detective Williams ultimately decided to anonymously send Tim Kono's phone to Mabel, in the unlikely hope that the podcasters might be able to find something her bosses can't ignore.