I'll take this opportunity to plug Martin Ross' great web site, "Just One More Paragraph", a collection of Columbo "fan fiction" featuring some very good, original "Columbo" stories and scripts by talented writers, some of whom are regular visitors to this Fan Forum.
This discussion particularly puts me in mind of that site's first contribution, "Vengeance Is Mine" by Eric Paddon -- a follow-up to "Presciption: Murder," set many years later.
Yeah, many of those folks are in their eighties. Of course, the murderer(s) probably wouldn't chance a death sentence at that age . . . their motive would be revenge and only revenge. The producers would have to be careful if several colluded in a murder scheme to avoid it becoming an "Over-the-hill-gang caper" beneath Columbo.
Many thanks for the plug, Ted! Of the four Columbo fanfics I've written, that remains my favorite just because I liked the idea of bringing Columbo full-circle as it were.