Funny, I alaways love this final trick in "Deady State of Mind", it really contain a fabulous twist, in fact it's one of my favouire end. As for "Double Exposure", I enjoy the whole episode and the interaction between Falk and Culp, but the ending is just far from satisfysing. Actually if the writer could come up with a better ending, I would give it full score.

I've always thought it strange that Columbo doesn't investigate the state of the gatepost into which Donner crashes his car (possibly after the blind man tells him there has been an accident).

Then the final clue could be something like a paint trace from Donner's car left on the gatepost. And the corny final line could instead be, "I don't have an eyewitness, but I do have an earwitness".

In episodes such as this, Columbo fails somewhat in his duty in allowing a second murder to occur at all.

In 'Double Exposure', why Kepple doesn't dispose of the incriminating piece of evidence earlier on is beyond me.

I always liked this episode and the ending despite the certain weaknesses people have mentioned. However, the ending is not really plot-specific...they could have thrown a blind man in any episode. Maybe it would have been better if the ending had been related to the plot to murder Nadia, rather than focusing on the manslaughter-ish killing of Karl.