Factual error: Dominic Wingrave says "it took me 6 years to do the math." Not something any British person would say - in the UK it's always "maths."
Factual error: Despite taking place in Massachusetts and many of the cars having Massachusetts license plates, none of the vehicles has the required annual inspection sticker on the lower part of the passenger side of the windshield.
Factual error: The show, which is set in California in 1947, mentions the gas chamber, lethal injection and the electric chair as methods of execution in the state. Two murderers are sentenced to death by lethal injection and one is depicted being instead executed in the electric chair, which the governor states has been brought out of retirement for the occasion. In fact, California adopted the gas chamber as its sole method of execution in 1937 (having previously used hanging). Lethal injection was not used in the United States at all until 1982 and not adopted in California until 1993 (becoming the prime method in 1996). California has never used the electric chair.
Factual error: In Massachusetts, Atticus, Leti and George are attacked by the local sheriff and his deputies, who are patrolling the county roads. In Massachusetts, sheriffs run the county jails, but they do not (and did not) handle routine policing, which is the responsibility only of municipal police departments.
Factual error: A man enters a bank and begins firing his Glock 9mm pistol. A few of the men he shoots, jump up in the air after the rounds impact their bodies. Bullets hitting a body will never make it jump, or fly in the air. (00:00:01 - 00:01:46)
Factual error: A British soldier in 1940 says he was educated at the University of Warwick. The university wasn't founded until 1965.