Plot hole: When Jessica is arrested for the murder of the enemy agent. Her purse is confiscated. It was reported stolen by Michael Haggerty. But throughout the whole show none of the cops looked at her ID. Besides that she's a famous women and someone at the police station would definitely know who she is.
Visible crew/equipment: When the sheriff and the mayor meet at the fix-it shop, the filming crew plus the boom mic pole are reflected on the side of the red car.
Revealing mistake: All the shots of snow falling, mainly when Gunnar is about to be killed, are a very obvious crappy footage of flakes falling projected over the footage of the show. Not a single flake falls on the objects nor the people.
Something Borrowed, Someone Blue - S5-E9
Revealing mistake: When the corpse lies on the bed the pad under the clothes where the thermometer is stuck protrudes.
Something Borrowed, Someone Blue - S5-E9
Audio problem: Whenever someone is walking on a rug the sound we hear is of footsteps on a tiled floor.
Something Borrowed, Someone Blue - S5-E9
Continuity mistake: In the kitchen the police officer loosens his tie, but from the side shot it's still tight.
Fire Burn, Cauldron Bubble - S5-E13
Factual error: The only instances of "witchcraft" or "witch trials" in America were in Salem, Massachusetts. There were none in Maine or anywhere else. The Salem witch trials spanned 15 months, from February, 1692 to May 1693. Over 200 people were accused of witchcraft, but only 30 were found guilty. Of the 30, 14 women and 5 men were executed by hanging and one man, Giles Corey, was executed by "pressing." Another five died in jail, but none were burned at the stake, which was a punishment unique to Europe.
The Sins of Castle Cove - S5-E17
Visible crew/equipment: When the hairdresser buys a lot of books and leaves in her car, a huge screen and scaffold are reflected on the rear window.
Trevor Hudson's Legacy - S5-E18
Visible crew/equipment: When the woman picks up the hitchhiker the filming equipment is reflected on her car.
Trevor Hudson's Legacy - S5-E18
Revealing mistake: There are 2 scenes involving Jessica inside a car. In the first one the car drives calmly as seen from the outside shots, but from the shots inside the car is speeding. When the episode is about to end the car speeds to the police station and now the exact same projection is played, though this time it makes sense.
Mirror, Mirror, On the Wall (2) - S5-E22
Other mistake: When the sheriff finds the apple, the bitten side has a fresh white colour, instead of the brown colour it should have after the many hours passed.
Mirror, Mirror, On the Wall (2) - S5-E22
Continuity mistake: When Eudora arrives at Jessica's home to apologise, she's wearing a pair of gloves. A shot later, the gloves have vanished.
Chosen answer: This is the very reason my brother and I used to jokingly call the show, "Murder, She Caused." It's amazing she was ever on anyone's guest list for a party, given the likelihood someone would end up deceased. As to your question, most of the time, Jessica Fletcher would have had an air-tight alibi, as she was in a room full of people, or her whereabouts were accounted for when a murder occurred elsewhere. It also seems to me that there were episodes where she, purely with respect to opportunity, could have been a suspect. I believe she even acknowledged that as a logical possibility from time to time, even though she knew, of course, she was not the killer. However, the investigation would obviously rule out the possibility of her involvement, eventually.
Michael Albert