I just realized, when Dabney puts the poison in the bottle with the syringe , that champagne is under pressure, wouldn't it leak out the hole he just made?
AAHH HHAA! this is the episode I was trying to think of... While setting up a simulation of a speeding ticket on a traffic cam, Columbo tells the tech, "in all the years I've had this car, this is the first time I've had the top down"... but we all know the top was down in 'Last Salute to the Commodore' in that strange scene with 15 people piling into Columbo's car.