Garak's disdain for human detective fiction is, of course, well-documented. But I think he would find Columbo the exception
Consider:
Guilt is a given, the suspense comes not from "who did it" but "how can Columbo prove it."
Columbo is always correct. Never does he get the wrong person.
Columbo flagrantly disregards due process and "rights" (most of his cases would easily be overturned in court but that's not shown)
Columbo is a master of obfuscating stupidity, something Garak would appreciate
Columbo is extremely loyal to his family
Watching it would absolutely give Garak access to more silly mannerisms with which to annoy his twink boyfriend.
