During the opening at the party, the violinist and pianist are playing Felix Mendelssohn's violin concerto. But they begin with the third movement. Later, when Nick is there, they play the first movement. No musician would have reversed the movements, but the director, likely not knowing the difference, must have shot the Nick scene first.
Most women wore long dresses at Lauren's party, but one women entered the house in a short, gold-spangled cocktail dress with matching hip-length open jacket. At the end of the party, she left in just the dress -- with a fur coat/jacket over her arm.
When Lauren is adjusting Columbo's tie in the department store, his jacket is buttoned all the way up. Lauren then walks away to look at a hat. Columbo turns to follow, and his jacket is completely unbuttoned.
In Columbo's scene in the restaurant with Barney (approximately 1:07 in), for two minutes of their conversation, a pencil appears and disappears from Columbo's right hand several times as the camera angle changes from his left to his front and back.
When Columbo transitions from apartment 2A to 3A, the red mug and the boiled egg swap hands.
Columbo attempts to determine why the ice melted in the small refrigerator; he determines the top outlet is connected to a different circuit breaker than the bottom outlet. Standard duplex electrical outlets sold in the U.S. for many decades allow for "split outlet" wiring. This means the top and bottom receptacles can be powered by two different sources of electricity. Typically this is to allow one outlet to be switched (typically for a plug-in lamp controlled by a wall switch), but what is shown here is easily accomplished for whatever reason, by a home do-it-yourselfer with outlets sold anywhere inside the U.S.. Anyone who has ever stayed in rental property where a clock radio was inadvertently plugged into a switched outlet, and then turned the radio off or on with the click of a switch, can vouch for how easy it is to not realize what has been done within the walls.
In the opening credits, the water from the fountain outside Lauren Staton's house defies gravity and flows back into the fountain, revealing that the shot is being played backwards.
(At around 17 mins) A few seconds after the buzzer goes off, the dead man blinks his eyes.
The first time Lauren called Lisa, she dialed only six numbers.
Columbo is told by the telephone co. worker that all 12 calls from Lisa went to 818-555-7247. As he later watches Lisa exit her apt., he looks at the phone bill printout, on which appears to be written in big black ink, 818-565-7247. However, upon closer examination, the 'incorrect' digit is actually a five where the bottom loop has been drawn too far.
Lisa Martin waits with the corpse, which is covered with an electric blanket. A few seconds after the doorbell rings, the dead man blinks his eyes. The camera angle and the actor's heavy eyelids create a startling effect as he bats his lashes. Apparently the actor's eyes are open except for the blink, which is puzzling since the dead body was seen earlier with his eyes closed.
Columbo comes into the crime scene and picks up an ashtray to hold shells from his boiled egg. When the deputy hands him the coffee he requested, a detective wearing gloves is dusting another ashtray for fingerprints. No one admonishes Columbo for entering an active crime scene with no gloves and handling what could be evidence; i.e., the detective is dusting one ashtray for prints, but says nothing to Columbo about handling the other without gloves.
Lisa's neck scar isn't present in the wash room.
Lauren turns off the power to the living room so that the lights won't work when Nick and Lisa walk in. Lisa turns it back on right after the murder. The elapsed time wasn't enough to allow the freezer to thaw.
During the credits, when Armando Pucci's name appears, a boom mic is visible at the top left of the screen.
Columbo enters and searches Lisa's room after she leaves and removes photos with no legal authority. He had no search warrant and insufficient evidence against her to have obtained one, and made copies of them before she was even brought in for questioning.
When Columbo arrives, the medical examiner announces the time of death and that Nick was shot in the chest with an exit wound in the back. When Lauren shot Nick, his back hit the door where he hesitated and then fell to the floor. There was no blood on the door behind him despite there being an exit wound.
(at around 47 mins) Columbo refers to Nick Franco as "Mr. French".