I totally agree with you. That is the first thing that bothered me; I rewound to the part where Trish disclosed to the killer that she suspected him of murder. She also added that he used her to kill the girlfriend. Trish said to the killer that he borrowed her car while she ran around on errands doing research. However, why would Trish wear a mask while running the errands, unless he had to be on a site where people could see him, but not talk to him? It doesn't make sense is
illogical. This is the only time I have ever found such an error or unbelievable error in "Columbo". I lov'em and the show, so it doesn't bother me, but it is very surprising.