The Los Angeles Chronicle article regarding the murders reads, "Two Die in Bizzare Double Killing", misspelling "Bizarre".
When Lt. Columbo is searching the car containing Teddy McVeigh's body, the murder victim can be seen to be breathing.
The rodent Columbo pulls out of the dumpster is a rat with a long tail, but the photo he later shows of ostensibly the same animal is that of a field mouse with a much smaller tail.
Despite the fact that Teddy McVeigh was sitting in his car when he was shot, there is absolutely no blood anywhere on him or in the car.
After Fortelli tells Graham that he wants ownership of his farm and he leaves to get into the stretch limo, the reflection of the boom mic can be seen in the window.
When Graham McVeigh calls Columbo in a panic, he describes the restaurant as being "just east of Wilshire". Wilshire Boulevard runs east-west, so a location wouldn't be described as "east" of Wilshire.
With the way the killers confession was given, it would have certainly been thrown out as it was made under duress and not willingly.
When Columbo is brought to the mob boss, the boss starts speaking to him in Italian. Columbo doesn't understand Italian to the mob boss's surprise, as he has an Italian surname. In Death Hits the Jackpot (1991), however, Columbo spoke Italian fluently at the funeral.
Columbo asked the brother for a cigarette but he always smokes cigars.