Here's what he *should* have spotted...(spoilers)

Clearly Columbo wasn't that good a detective in those early days because he'd have spotted that there was glass on TOP of the body - e.g. Gene Barry strangles wife, lowers her to floor in front of patio glass, then goes outside and breaks said glass, showering her in fragments thus proving that wife was attacked prior to window being broken. That makes Barry the murderer, and would have wrapped the whole thing up in five minutes.

The second thing he missed is that the last person to touch the light switch in the apartment was Barry after he kills her. For the alibi to have worked, his wife supposedly came back from airport (switching light on), then later switched it off when going to bed. Again, show would have been over in five minutes when Barry's prints were shown to be the last on the switch (oh, and notice he'd taken the gloves off by then so his prints would have been last on the switch - particularly as the cleaner came in during daylight so wouldn't have touched it)

Columbo a master detective? Pah! This pilot was a badly thought-out screenplay that was laughable in many places and quite rightly wasn't picked up.