Continuity mistake: Most of Season 1 takes place in January of 2006, while Season 2 takes place in March of 1979. Molly mentions near the beginning of Season 1 that she's 31, and her father confirms this in episode 10 by mentioning that she was 4 years old during the events of the Sioux Falls massacre (season 2). In season 2, Molly's mother mentioned in episodes 1 and 4 that she's 6. It's also revealed in a flashback scene in episode 10 that she graduated high school in 1991 (most people are 17 or 18 when graduating high school). If you do the math, you'll see that there's an inconsistency in her age between Seasons 1 and 2. Apparently, 2 years were added to her age in Season 2.
Mommy's Little Monster - S2-E7
Continuity mistake: Miss Kringle's head is canted up and to the right as she lays on the gurney in the morgue refrigerator, but when Edward Nygma pulls her out, her head is facing straight up. Subsequent shots of her in the refrigerator her head is canted up and to the right.
Continuity mistake: During the street scenes it appears to be fall with leaves on the ground, grass green and streets and sidewalks dry. However, when police raid the park worker's house there is snow on the house roof and on the ground. When the police stake out the same house, there is no snow on the house roof or ground. (00:36:00 - 00:41:00)
Episode #1.6 - S1-E6
Continuity mistake: The district commander wears the rank insignia of a chief superintendent up until the final episode, when he suddenly appears with the insignia of the lower rank of superintendent.
Other mistake: Dr. Wade is the ME for Jefferson Parish. Most of the victims are found in Orleans Parish. Not her jurisdiction.
The Secret Fate of All Life - S1-E5
Continuity mistake: The first time we see Detective Cohle being interviewed by the other two detectives, two of the beer cans on the table in front of him completely vanish between shots when he asks to see the rest of the discovery file.
The Legend of Curtis Ballard - S2-E3
Factual error: In the first flashback scene of Ballard serving a Mormon mission in Lithuania, he laments that he has been on his mission for 18 months and has yet to baptize a single person. In a later flashback scene when he and his companion are visiting the prostitutes, he states that he and his companion are 19 years old and they should be in college, going to parties, getting drunk, getting laid, etc. Instead of serving missions. These scenes take place in 1991, at which time young men did not serve missions for the Mormon church until after they turned 19, so if Ballard had already been on his mission for 18 months, then he should have been at least 20 years old, and closely approaching 21.
Continuity mistake: In S:1 Ep.10 Maddie says she'll be 15 in a week. Season 2 picks up 6 months later. In S2ep5 Bosch uses Maddie's birthday to access a computer. Password is 01/10/01. This makes the date sometime in July of 2016. Then in S2ep6 George Irving is killed, and the end of watch broadcast lists his date of death as 7/24/2015. This error is reinforced in S2ep10 when they show a plaque being mounted to honor George.
Character mistake: The brigadier wears a regimental cap badge. Colonels and brigadiers have their own cap badge.
Episode #1.3 - S1-E3
Other mistake: The publican asks for payment for some drinks, saying "One and six, please", meaning one shilling and sixpence. The subtitles say "One-o-six, please."
Factual error: Congressman Tate and his brother are on the shooting range. They are wearing high-tech electronic earmuffs that block harmful noise like gunfire while amplifying speech and other low-volume sounds. Although, they are wearing high-tech earmuffs, they both have an ear exposed so they can hear each other talk. (00:13:00)