Throughout the film they are addressing the judge as "your honour". That's American. In England a male judge is addressed to as "My Lord". Also Americanisms, Janet is hanged with an American-style coiled noose, not the simple eyelet noose used in Britain, and the hood put on her is black (as in America) not white (as in Britain).
A witness would be required to remove their glove when touching the Bible when taking the oath.
In the close-up of the Evening Standard newspaper that Romaine reads, Janet the maid's surname is quite clearly printed as 'Mackenzie.' Though this is the surname Agatha Christie used in the original story, in the adaptation Janet is called 'McIntyre' both in the credits and by other characters.
The gramophone in episode one playing a 78 shellac record has the sound of a 33rpm vinyl record supposedly at the end of the track, but the visual shows the needle about a third of the way into the track which would have music etc.