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.