Factual error: Nick tells fellow vampire Aristotle, "You still owe me for that time at the Battle of Hastings." Nick was brought across in 1228, or so the intro told us every week. The Battle of Hastings, as any British school kid knows, was fought in 1066, over 100 years before Nick's mortal birth. (00:29:30)
Factual error: As the creepy "Nightcrawler," master vampire LaCroix taunts Nick via his CERK radio broadcasts, which Nick listens to on his Cadillac's car radio. Except, CERK's studio sign says it's an FM station. And Nick's Caddy, supposedly a '62, still has its factory radio (we get lots of good close-ups of that), which in 1962 was strictly AM. So how was he receiving LaCroix's station?
Factual error: Though she wore medical smocks and occasionally a baseball cap to hold back her hair, Natalie was never correctly attired when she performed her autopsies. In fact, she usually worked with her hair loose and hanging down over the corpse, which may have made her look prettier, but is a serious breach of forensic etiquette that could contaminate the evidence. Even the best-coiffed coroners still have to wear sterile caps and gear.
Factual error: The murder victims, all Catholic, are specifically said to have "all worn crucifixes." But the jewelry Nat hands Nick as evidence, the cross that burns his hand and the necklace Magda later gives him are all plain crosses, not crucifixes. (The former is unadorned; the latter has a Christ figure on it.)
Factual error: Nick tells Nat about his past life as an assistant professor in the U.S., and refers to himself as "a certain indigenous vampire." Nick wasn't indigenous (native) to either the US or Canada, where the show was set. He came from Brabant, now part of Belgium. They were probably trying for "itinerant" (wandering), which would accurately describe Nick's long life.
Factual error: In the first scene, Dr. Dana says the asteroid heading for Earth is 5 miles wide, "larger than the one that caused the dinosaur extinction." The asteroid that did in the dinos is estimated by most scientists to have been 6-8 miles wide. (00:03:00)
Factual error: Nat's god-daughter Cynthia Luce is buried within a few days of her murder with an elaborate headstone already in place. (In reality, headstones take months to produce.) But the wrong name is carved on the stone. It reads "In memory of Cynthia Lambert." (00:43:30)
Factual error: At the end, Nick recites the "you have the right to remain silent" spiel to Rita as he arrests her. Suspects in Canada, where this show is set, are not "read their rights." That's a U.S. law (the Miranda Act) and it isn't observed north of the border. (00:41:45)
Factual error: At the very end, Bridget Hellman is buried with a fully-engraved headstone in one just one day's time (which happens only in tv & movies: the process takes months in real life... er, death). She also spontaneously returns as a vampire without being "brought across," a violation of series canon, and she comes back mysteriously sporting 3 times more hair than she had as a mortal. (00:43:10)