The Old Head - S1-E8
Continuity mistake: In the scene where LJ comes to visit Lincoln and admits to breaking the coffee table, LJ's hand moves between shots. When Lincoln is shown, you can see LJ sitting in front of him with his chin resting on his hand. When the shot changes to close-ups of LJ, his hand is down and completely out of the shot. (00:08:10)
The Old Head - S1-E8
Continuity mistake: In the episode "The Old Head" when Michael gives the cat back to Westmoreland, from the side, the cats paw is on his shoulder but when the angle changes to the front, it has moved down to his chest. (00:17:45)
The Old Head - S1-E8
Continuity mistake: Michael hands out sledgehammers at the end and passes one to Abruzzi with the head facing down. Abruzzi then passes this one to Lincoln but the head is now facing up. (00:39:00)
The Old Head - S1-E8
Continuity mistake: Bellick visits Westmoreland in his cell and puts his cigs in his pocket as he walks into the cell. When he sits down, he puts the packet away again. (00:25:40)
The Old Head - S1-E8
Continuity mistake: Kellerman kills LJ's step dad who subsequently falls on top of Kellerman. When Kellerman is trying to push the step dad off himself his tie is over his left arm. When the shot changes, his tie is now under his arm. (00:23:30)
The Old Head - S1-E8
Continuity mistake: We see a close up of LJ's phone and the aerial is on the phone's right. Cut to a long shot and its now on the phone's left. (00:41:00)
The Old Head - S1-E8
Continuity mistake: The level of the tools in the guard's room changes between shots. (00:39:10)
Answer: Because of coincidence.