Continuity mistake: In the psychiatrist's office, Columbo strikes a match and lights his cigar. Two seconds later, we switch to a closeup shot and the match is about six inches away from his cigar, which he proceeds to light again. (00:44:15)
Continuity mistake: At the very end Fleming sees the dead body of his girlfriend being hoisted onto a gurney - she is soaking wet, having been hauled out of the swimming pool. Later we see it is a policewoman acting as a stand-in in order to fool him into talking - and after a few minutes under a blanket on the gurney she, her bikini, and her hair are all bone dry. Not only that, her hair looks like it has just been styled and her makeup is perfect.
Continuity mistake: When the girlfriend speaks to the cleaners the phone is on the bar, and then they leave for the airplane. When Mr. Fleming comes back the phone is on the table.
Continuity mistake: The chess set on the table is in a different position after the murderer returns from Acapulco as opposed to right before he murdered his wife.