Jake and the Fatman is a very smart show in many ways. One of the smartest aspects is that the crime takes place as much in the criminal's head as in a particular time and place.
That isn't to say that the show is psychological mystery. It is very much a whodunnit/howdunnit action show. But the motive can be what people imagine as much as what actually takes place.
Dorothy Sayers understood the power of the imagined grievance when she addressed the impact of jealousy on a relationship. Agatha Christie also understood it, particularly the way an idea can become a story in the brain. With several would-be murderers, Poirot gently makes the point, "You imagined a murder--that doesn't mean you committed it."
The entire world of love and abandonment that Elinor imagines in Sad Cypress (over a fiance who isn't worth so much emotional investment) is a poison that is eventually purged. She never goes as far as she thinks she might. (The Poirot version, though well-acted, misses the point--the scriptwriters insisted on making the affair a matter of actual sex rather than emphasizing that Elinor has invented a more passionate fiance than she has; her identity, her imagined future, is on the line, not an actual flesh-and-blood relationship.)
Several of the criminals in Jake and the Fatman act not based on good judgment or objectively collected information but on that type of invented story. They think that there were let down, abandoned by a lover when, in fact, they never were.
In the first season episode "Fatal Attraction," a wife and stepson kill off the husband/father. Jake then uses the young man's competitive nature to drive a wedge between him and the wife. When the young man apparently disappears, the wife is easily persuaded that he gave her up--which he never did.
Likewise, a later villain believes that his girlfriend gave him up when Jake gets her a singing gig. But she never did.
The police don't have to manipulate these villains. The singing gig, for instance, is completely legitimate. If the girlfriend had held on in the first place, rather than giving up and resorting to crime, she might have broken into the field.
For the boyfriend, the legitimate nature of the singing gig underscores his insecurity. He knows--as does the stepmother with the stepson--that the lover has a less criminal option. Maintaining a relationship through dodgy behavior brings the foundation into question. It backs the idea that humans are attuned to fairness versus unfairness at a basic, non-taught, "natural" level. Something has got to give.Or, perhaps, the reaction hints at a fundamental belief (however avoided through sophisticated philosophizing) that what goes around, comes around. The villains' stories about others
and themselves and the world have convinced them of a particular
outcome, and that's the outcome that comes about.
From a romance point of view, it underscores the inherent vulnerability of love. Love me? Really? For how long?