Continuity mistake: The underground car seen in the CCTV video is from the Jubilee line, but is meant to be the District Line. It's also different from the one where the heroes defuse the bomb, which is an actual District Line train (D stock). The rounded doors is the most visible proof.
Continuity mistake: When Sherlock steps out of the taxi on Baker Street three extras walk by. First, it's a lady with her back to the camera, wearing a dark jacket, purse, boots and a dark curly hair. Next, the two women walking towards the camera. Notice the blonde one on the left with the pony tails, dark jacket with the multi colored cloth at the bottom, and grey pants. Fast forward to when the taxi pulls up to take Sherlock and Watson to the the crime scene. As Sherlock opens the taxi door, the same first lady with the curly hair and the blonde with the ponytail are now walking together in the same direction the blonde was walking when Sherlock arrived. (00:12:58 - 00:17:51)DirtyP428
Revealing mistake: The banker shoots himself with a Sig 226R. When you see it lying on the bed it has a screw missing from the grip. In the first episode, Watson has a gun in his desk drawer. It is a Sig 226R also with a screw missing from the grip. Obviously they only have one prop gun.
Factual error: Sherlock takes pains to explain in detail that he will deliberately corrupt the magnetic code stripe on an access control card he intends to use to enter the elevator to the villain's penthouse, by carrying it next to an operational cell phone. (This is possible due to the low frequency magnetic field from a phone's vibration motor.) But when he actually goes to access the elevator, he simply touches his access card to the reader instead of swiping or inserting the card through a slot, which is how a magnetic stripe reader would operate. The elevator uses an RFID proximity reader, not a magnetic stripe reader - a phone wouldn't corrupt an embedded RFID tag.Stringman
Continuity mistake: In the opening scene when John is going to the refrigerator, a white skull can be seen on the left side of the kitchen table amongst all Sherlock's science equipment. When he closes the refrigerator door again after discovering the severed head, the skull has disappeared. As he's leaving the kitchen, the skull reappears. (00:03:25)Chitarra10
Character mistake: While the original Sherlock Holmes is famous for making water-tight deductions, the one in this episode does not quite live up to that standard. He declares someone a "compulsive cheat," because: "Waterproof cover on his smartphone. Yet his complexion doesn't indicate outdoor work. It suggests he's in the habit of taking his phone into the shower with him, which means he often receives texts and emails he'd rather went unseen." There are far too many problems here. (1) The only type of complexion that indicates outdoor work is sunburned. We don't have water-soaked or snow-frozen complexions. So, yes, he might work outdoors. (2) Indoor work may also deal with water, e.g. plumbing, dish washing (note what the accused man is doing!), water purification, lab work, etc. (3) Some people might just purchase a waterproof cover as a precaution. Some might receive it as a gift. Some may receive it free during a bulk purchase. (4) Not everyone who takes his or her phone into the shower has fidelity problems. They might want to listen to music, be up-to-date with the stock market, or, if I may use a euphemism, might want to have some quality alone time. (00:12:35)FleetCommand
Character mistake: Lestrade mentions that there could be some "poor sod covered with semtex on the streets somewhere" when talking about Moriarty's victims, but semtex does not go off via gunshot, much like C4. But that is what happens when one of the victims dies however, so the explosives are not semtex.
Character mistake: In the opening scene, Sherlock makes a point to correct Barry's poor grammar. But later, when talking to Watson, Sherlock uses poor grammar by saying "who's sleeping with who." It should be "who's sleeping with whom." Not a mistake Sherlock would make.Bishop73