Plot hole: When the watch is sucked to the island by the magnet, where was the sailor that the watch was attached to?
Plot hole: When Mike Walker is out looking for his son Connor calls Satch and asks, "What's up with Mike?". She couldn't know that there was anything up with him, she left before he heard his son was missing. Had she called Walker on his cell, he would have explained what was going on, as he was very eager to tell her. Obviously a set-up so that Satch could tell her that the boy was missing.
Plot hole: During Ryder's report, as Bruce and company watch it on TV, the camera suddenly zooms in on Joker standing on a catwalk above Ryder, and none of the crew, especially not the camera man who caught the villain, makes a comment about this. They may have thought the Joker (or rather an impersonator) was perhaps a surprise gag in the show, but since this is supposed to be a serious documentary report, it is still strange that they wouldn't point it out.
Deathfist 5: Major Crimes Unit - S2-E15
Plot hole: The whole case is solved because of astronomical coincidences, since the culprit is someone related to the actor, who is teaming up with the investigators for an entirely unrelated reason. Los Angeles is kinda too big for this sort of 'coincidence'. Moreover, had they committed the crime any other day (there was no particular reason) there would have been no connection.
Plot hole: Episode 1: All passengers on cruise ships have a passenger card with their name and cabin number imprinted. They are not just identical key cards like in hotels.
Plot hole: Early in the show, Jamie is in a patrol car escorting a witness when they are attacked by several guys in a van. The side windows of their cruiser seem shatterproof and withstand many bullets, while the rear window is shattered immediately. NYPD cruisers do not have bulletproof windows.
Plot hole: It's stated multiple times that the Semper Apex server room is protected from wireless signals, but Sofia's team sneaks in and plants a "ghost jack" with a wireless transmitter on it, which they say is slaved to an IP address. Except that wouldn't work in the server room. There'd be no way to get a signal to or from it.
Plot hole: To identify the owner of a severed leg, Pride asks Loretta if she can guesstimate the body's general build by the foot's boot size. A much simpler way would be to swab for blood where the leg was severed and run it through the military DNA database.
The Countess - S1-E4
Plot hole: Rockford and Carl Brego are punching and kicking each other on the beach. Someone shoots him down with a rifle. The INSTANT Rockford goes to check out if he's still breathing, two people randomly happen to walk on him popping over from behind a rock as they were having a super casual and amused chat, but see Rockford by the shirtless brute and make a horrified face. Later in the episode the two identify Rockford and say that it looked like the two were fighting. Their facial expressions at the time don't make sense as depicted. Even if we assume that they did not see anything at all and they played it up/filled the blanks in their mind later, the two are not deaf and yet they were not perturbed or curious in the slightest after the loud bang of a gunshot. The way the scene was shot, the only thing tipping them off about anything was seeing Rockford over the corpse (which had barely a small dot of blood visible at the time and would hardly tip anyone off at first sight). (00:18:45)
Episode #1.3 - S1-E3
Plot hole: The killer is meant to create the perfect crime, but the angle of the shot would make obvious to any forensics examiner that it's a suicide. There is practically no possibility for a person supposedly positioned across a long dining table to kill someone else with a shot under the chin. (00:55:50)
The Case of the Deadly Toy - S2-E27
Plot hole: Claire Allison spends the night in an upstairs bedroom in the Jennings' home. In the middle of the night, she opens a walk-in closet to get another blanket and finds a small printing press. Later in the day, Claire returns to the home, accompanied by Perry Mason, who tells Mr. Jennings that Claire has received threatening letters from Mrs. Jennings' former husband, who still has a key to the Jennings' home, and the printing press may have been used to address the envelopes. Mr. Jennings says, "We'd better investigate" and immediately goes upstairs and opens the closet, even though neither Claire nor Perry Mason said where Claire saw the printing press.
Plot hole: Kevin is keeping his true identity that he is a police officer from Celeste while Intelligence is investigating a murder committed by one of her art students. Although Kevin is hiding his identity from her, he participated in the daylight search of her art studio looking for the murder weapon. How was Celeste not present during the search of her studio or not aware of the search happening without Kevin being revealed as a police officer? (00:54:04)
Plot hole: It's revealed that the gym owned by Ray and Terry is a front for Ray to launder his income. This is why he doesn't want or can't sell it. Any person auditing that gym would know it doesn't bring enough income if the floors are in disrepair and the equipments garbage as Terry tells Pie when he gives him money to fix it up after Mickey pays him. Ray runs a consulting firm, he could launder millions through consulting, he has an office with employees. Get vending machines, anything that's cash. (00:42:00 - 00:44:20)
Mondays Are for Murder - S2-E13
Plot hole: In an effort to keep Glenn's death as quiet as possible, Higgins hires a private pathologist to do an autopsy to see if there were any foreign substances or poisons in his system when he died. A few scenes later it is revealed that Glen was undergoing chemotherapy. How is it possible that the pathologist missed the cancer and the chemo treatment in his investigation? What he found was an excess of antacids.
Episode #4.1 - S4-E1
Plot hole: When DCI Roz Huntley kills Forensic Coordinator Tim Ifield the crucial piece of damning evidence is her DNA under his fingernails after scratching her arm. Problem being, at the time of his murder, he was wearing surgical gloves. (00:56:40)
Episode #2.6 - S2-E6
Plot hole: Laura is spotted at an airport where it is assumed she goes to Edinburgh. Although she mentioned later on she broke her bail by leaving the 30-mile radius by her bail conditions. This wouldn't have been possible as part of her bail was to surrender her passport.
Casualties - S2-E14
Plot hole: When Bradford and Chen arrive at her apartment to see the damage her newly adopted dog did, she discovers the dog ate her roommate's varsity jacket, but she had to turn the doorknob to open the door; there is no way the dog got into that room if the door was closed.
Farewell My Beloved Witch - S1-E3
Plot hole: Lupin was captured by chance, and he did not plan for that, nor he seemed to have previous knowledge of Stern's appearance, but he escapes regardless using a Mission Impossible-like perfect mask of him. He also somehow kept his own blazer, tie and shoes underneath the uniform and boots he stole and wore. (00:16:00)