Factual error: On July 4, Kya waits for Tate, watching the sun set and the fireworks at night. She falls asleep on the shore and wakes up in the same position, watching the sun rise. So the sun sets and rises in the same position. (00:55:40)
Factual error: A .22 shot would be 120-140 dB, muffled with a pillow down to 100-120 dB. Only one person heard the second shot? No one heard the third? Plus at the end there's no way a .22 could pass through a male chest cavity, and halfway into a female chest cavity - it's too low power.
Factual error: During the storage unit robbery in the beginning of the film, simply knocking the combination dial off the safe would not have caused the bolts to suddenly retract. It would defeat the entire purpose of having a combination lock. Even inexpensive safes have mechanisms to prevent this from happening.
Factual error: Norma Jean's mother is driving away from the house onto the street. She turns left and crosses a yellow dividing lane in the middle of the street. It is supposed to be 1933. But these yellow dividers did not come into existence until the 1950's.
Factual error: The owl that JP was looking at made a "who who" sound. The owl may appear to be a Snowy Owl (one many people are familiar with), but it is a Barn Owl. Barn owls are not "true" owls and it is the true owls who "give a hoot." Barn owls don't hoot; they make a screeching or squealing sound which can be piercing (and eerie to some people). (00:32:50)
Factual error: Rose's legs were paralyzed, but when she was dragging herself on the floor, she occasionally used her feet to help propel her body forward (and moved her feet downward) - something she would not be able to do if her legs were paralyzed. (00:33:40)
Factual error: The Artist lit a match and candle in his cell. Both are contraband in prison (especially for someone scheduled to be executed). Matches pose a risk of fire/arson and deliberate burning injury or death to a person. Candle wax can be used to prevent cell and other prison doors from locking, creating an escape risk. Also, The Artist's prison cell appeared to be much bigger than a master bedroom (standard size 14'x16'). Prison cells are around 6'x8' or 7'x12'. (01:17:45)
Factual error: Doctor Key tells Mary, "If you pose a threat to those around you, we will be forced to keep you here [hospital] longer. That means your son will be placed in foster care." Family members, such as the grandmother and uncle currently taking care of Tony, are preferred before placement in foster care. Foster care is usually considered among the last resorts, not first, and only when there are no suitable family members or significant others to provide temporary care for a minor. [SPOILER: It isn't known that the grandmother and uncle aren't biological relatives.] (00:29:15)
Factual error: When Laura dropped Cody off at school, there was one boy (far left side of screen) wearing shorts. In 1950s (and later) California, boys were required to wear long pants to school (no shorts!) and girls had to wear dresses. (00:15:26)