3 ideas
Hannah Sharabi reports that her 16-year-old son Ofer did not come home. Detective Avraham Avraham at first tells her such boys usually return on their own, and only takes the case seriously once days pass. The investigation fixes on Ze'ev Avni, a neighbor, teacher and would-be writer who once tutored Ofer and eagerly inserts himself into the case, but the truth turns out to lie inside the household rather than with the conspicuous outsider.
An investigator who reasons from base rates, knowing that most missing teens come back and most crimes are ordinary, is usually right, and that realism is why he is trusted. The same prior makes him slow to act on the exceptional case and quick to settle on the most ordinary-seeming explanation.
A bystander drawn to an unsolved case can inject his own narrative into it by volunteering information, fabricating messages or shaping the investigators' questions. Because he supplies a coherent story, he becomes the most visible suspect and pulls attention away from the quieter, more likely source. Investigators, like readers, gravitate toward whoever offers the most compelling plot, not toward the truth.