Revealing mistake: In an early shot shown from the neighbor's house, it is established that the Spencers' house is quite a ways uphill. Some of the later shots where Claire is spying on her neighbors and looking at their home, the angle of view does not appear to be correct. The neighbors' house looks like it's a lot closer and more level with the Spencers' home.
Revealing mistake: After Claire and Norman drop their daughter off at school, that night, Norman is in bed with his laptop, typing, but not once do his fingers touch the space bar.
Answer: There's no rule about how a step-father is referred to. Caitlin may simply not consider him a father figure and is close to her real dad. Most step children call their step-parent by their first name, regardless of how long the parents have been married. Most likely it's a plot device so that the audience isn't confused about or doesn't forget that Norman is not Caitlin's real father. Some may be offended by a father killing his biological child's mother. It makes Norman less attached to either Claire or Caitlin.
raywest ★
I am not trying to be rude, but have you seen this movie? You say that Caitlin might be close to her real dad. He is dead. Claire was "touring with a baby" after he died, and then she met Norman. Hence why I found the situation a bit odd. Norman has been in Caitlin's life since she was a "baby."
Azalea
I saw the movie some years ago and don't remember every small detail. However, my main point was that calling Norman by his first name was a plot device to keep the audience focused on him not being Caitlin's biological father. This kept his character more detached from Claire and Caitlin, and made him less sympathetic. It showed an emotional/personal divide existed between Norman and Claire and her daughter. He has less resistance in killing Claire if they did not share a biological child.
raywest ★