Continuity mistake: There's a vase of yellow flowers to the right of the helium "Happy Birthday" balloon (and screen). When Ashley gets up to answer the door, she walks past the balloon and the vase of flowers should be visible but is not. (00:01:40 - 00:02:28)
Character mistake: In the highlighted newspaper article entitled 'DeFeo Son Accused' about the killings, the first sentence of the article ends with two periods. Also, in the 3rd sentence, the word 'psychiatric' is spelled "psuchiatric" with a 'u' instead of a 'y'. (00:01:05)
Visible crew/equipment: When Detective Hole enters the murderer's cabin you can see somebody running in the snow outside.
Character mistake: Set in Texas, the Sheriff threatens the wrongdoer with the gas chamber. Executions in Texas at that time were all by electrocution, namely by "Old Sparky," the electric chair. Texas has never used the gas chamber for executions.
Factual error: When the bank robbers pull the money out of the vault, they claim all the cash is from 1982. Yet most of the bills have large faces, which was introduced into rotation in 1996.
Factual error: Following the blowout, Sara's phone is shown several times as being connected to Wi-Fi with a full Wi-Fi signal. Being in the middle of nowhere, surrounded by hills, it's highly unlikely there would be a public Wi-Fi connection for her to connect to.