I think Alex benedict thought that no one was looking and he could of put on the carnation on his lapel but Columbo was there and as usual he was snooping around

If the action was good enough to repeat in "Matlock: Diary of a Perfect Murder" years later, it could not have been so stupid. What is the big difference between a carnation and a name tag anyway?

YM..I agree that Nelson Brenner and Alex Benedict come off as terrifically inept and stupid. Your reasons are valid. But in both those cases I have always chalked it up to the fact that they were just so overly confident that they would never get caught. Brenner had the "agency" to protect him, and Alex was just a cocky son-of-a-gun!

When "stuff" like that happens I attribute it to the murderers being first-timers. Remember that great speech Columbo has in Prescription: Murder when he says that even though a murderer may be brilliant, he has just one chance; but cops have done investigations hundreds or thousands of times?