Plot hole: When Beverly is killed the killer shuts off the main power switch which would have turned all the lights off in the house, not just those in the bathroom. (01:31:00)
Continuity mistake: When Danny Kincaid is at the beach, he is wearing green shorts when he is taking his shirt and shoes off, but he has blue and black shorts on when he goes into the water. (00:19:00)
Character mistake: Ottawa is misspelled "Ottowa" on Nicholas Jenson Davis wanted picture.
Continuity mistake: When Ron Moody runs into the sea in pursuit of a suspect trying to escape, he shouts at Jessica to "Get the package!" In the next shot we see Jessica reluctantly follow him in, with a clear waterline from a previous take showing on her dark overcoat/cloak.
Murder of the Month Club - S11-E10
Factual error: When Joellen removes the manuscript from the locker at the Yonkers bus station, you can see the address it was originally mailed too. The zip code is 10205. This is incorrect. All Buffalo, NY zip codes start with "14xxx" a zip code starting with "10xxx" would be much further down state.
Visible crew/equipment: When Trish picks up Jessica at the train station and her car leaves, filming equipment and crew members are reflected in the windows.
Funeral at Fifty-Mile - S1-E22
Other mistake: It's a clear day not a stormy night as it should be when showing the barn in the flashback. Look closely and you can see a clear sky through the barn walls cracks.
Continuity mistake: When the lieutenant notices the blood on the rug, there is a blurry stain along with several drops of bright red blood. In the close-up, the drops are gone, and the lighting shift makes the brown rug appear grey.
Continuity mistake: When Jessica tells the goon that the doctor went inside, the man is holding the car door. A shot later, he is no longer holding it. This swaps back and forth.
Continuity mistake: While driving Jessica home, the lieutenant's seat belt alternates between being buckled and unbuckled from shot to shot.
Continuity mistake: Salvatore spills wine on the table, but in the very next shot, the tablecloth is completely spotless.
Continuity mistake: When discussing her pregnancy, Denise's hand placement on her bosom changes in every single shot, shifting position from angle to angle.
Visible crew/equipment: When Carmine lies dead, a studio light is reflected in the bureau's mirror in front of him.
Plot hole: Jessica concludes that the widow is the killer because she was planning to try on a new dress at the same time she was supposedly about to flee to Italy. Her intention to travel abroad had been revealed only during a private family meeting and was never made public. One could assume that someone might have passed this information on to Jessica, but from the viewer's perspective, it functions as a straightforward deus ex machina, with no narrative setup or justification.
Continuity mistake: When Nicole tells Vaclav that she's engaged, the position of his hands is inconsistent: in the close-ups, they are raised, while in the wide shots, they are lowered. This alternates back and forth.
Ballad for a Blue Lady - S7-E9
Continuity mistake: When Patti Sue is serving ice cream, Jessica's arm alternates between raised and lowered positions across instant cuts.
The Return of Preston Giles - S7-E7
Continuity mistake: When Preston is having lunch with Ross, he places his hands under the table. In the following shot, they are back on the table, and he is then shown putting them away again.
The Return of Preston Giles - S7-E7
Audio problem: When Jessica and the cop arrive at the crime scene, their footsteps sound as if they are walking on a hardwood floor, even though they are stepping on a rug. (Spanish dubbing).
The Return of Preston Giles - S7-E7
Visible crew/equipment: When Preston leaves Jessica at the hotel, a large set light is reflected on the right side of the car. It disappears in the reverse shot.
Continuity mistake: When Jessica greets Fred at the inn, the way her napkin is folded on the table changes between instant cuts.
Answer: In a flashback scene, it was shown that he had a violent temper, so it stands to reason that he finally killed her in a fit of rage.