Episode #3.4 - S3-E4
Character mistake: DS Miles while in the chocolate shop tells Ana to go with "DCI Riley." Riley has the rank of DC, not DCI.
Episode #1.3 - S1-E3
Character mistake: Richie Gulliver is referred to as Rory Gulliver on the newspaper headline. As he's supposedly a very well-known Member of the Scottish Parliament, it's unlikely a newspaper would make a mistake like this.
Episode #1.2 - S1-E2
Character mistake: In the incident room Danny's height is written as 4ft 8inches / 112 cm. 4'8" is 142cm. (00:06:48)
The Prison Prep School Murder Case File 1 - S1-E10
Character mistake: To show how hard the top students are working at the prep school, we see one of them writing; "I was at the course of a eight-week intensive." (00:04:50)
Character mistake: The voice tells Tom that the alarm deactivation code is 47223. However, when Tom enters the code subsequently to deactivate the alarm, he only enters "4723." You can tell he doesn't enter a fifth digit because the keypad chimes each time a digit is entered.
The Hairy Scare of the Devil Bear - S1-E8
Character mistake: Velma says bears only have four claws. Wrong, they really do have five claws.
Smoking Gun - S1-E2
Character mistake: When the bad guys put the generator in front of the air vent, Nigel looks at the white smoke and pointing at it says "Carbon monoxide." Carbon monoxide is colorless, white smoke is mostly condensed vapor. (00:35:20)
Character mistake: In the epilogue, Charlie illustrates the relationship of mathematics to real life by discussing the golden ratio and its presence in a host of real-life situations, including the shape of a nautilus shell and the distribution of petals in a flower. These claims are disputed by some mathematicians (see http://en.wikipedia.org/wiki/Golden_ratio#Nature), and the one about the nautilus shell one is untrue (see http://en.wikipedia.org/wiki/Golden_spiral#Spirals_in_nature). It's possible Charlie is just repeating what he has read or heard without investigating it for himself, but this is uncharacteristic of him.
Character mistake: When Rich refers to the film showing Davis (decades ago), he figures they were in "Asia... Mongolia or somewhere." However, the film cannister had "Tibet, 1937" written on it - important enough to show the audience, but not for the character to read? (00:40:25)
Episode #5.3 - S5-E3
Character mistake: The chief baddie spells definitely as definately.
Character mistake: Nick asks Janette if she's ever turned anyone else into a vampire - an odd question, considering the fact that he already knows she has. He was there when she brought the baroness across in the 18th Century flashback sequence for "If Looks Could Kill." It's even odder that Janette tells him she's never done it, since she knows that Nick knows she has. Apparently, the only one not in the know here was the scriptwriter.
Character mistake: Elliot is sitting on the porch with his mother. He says dizziness could be a sign of a heart attack, or a cardiac spasm that could lead to a myocardial infarction. Elliot is an exceptionally well-informed kid who would know that a myocardial infarction is a heart attack.
Compromised - S1-E9
Character mistake: When she and OA meet Marshal Ackerman, Maggie is somewhat surprised to learn Damon Cruz was a federal witness. As a federal agent herself, Maggie surely would know that the Marshals Service's mandate includes the witness protection program.
Devil Music - S5-E4
Character mistake: When they pulled the bullet out of the wall of the Five and Dime, Danny says that it was either a .40 or .45 caliber. The .40 caliber was not produced until 1990, 37 years after the date the crime took place. (00:30:00 - 00:35:00)
Character mistake: When Collier is meeting all the 4400s at the reunion, Shawn calls Isabelle Maia by mistake. (00:31:10)
The Dark and Bloody Ground - S1-E3
Character mistake: Clyde Russell tells Rockford to meet him at his place in "Ambazac Road in Bel Air." The name of the street in real life is Ambazac Way. (00:38:20)
God Is in the Details - S2-E10
Character mistake: When Diane quotes the scripture, she says "Revelations." However, it's just "Revelation." Someone as smart as her who has read the New Testament (or heard it quoted) would know the correct word.
Character mistake: The brigadier wears a regimental cap badge. Colonels and brigadiers have their own cap badge.
Character mistake: Upon finding the Spanish flu virus missing, Hardison freaks out about it killing 50m people 100 years ago, saying it would be even more deadly today due to the higher population. There's no reason to think so - the death toll in 1918 was massively exacerbated by the aftermath of WWI. Not to mention today we have vaccines, plus most deaths then were actually caused by bacterial pneumonia, which today is easily treated with antibiotics.
Episode #6.4 - S6-E4
Character mistake: The character pretending to be Lt. Ellis refers to himself as First Lieutenant. That rank is referred to orally as "Lieutenant", not "First Lieutenant."