When John picks up Dawn at Sally Hansen's house, she has with her the little dog, but when they leave running down the stairs, she has nothing in her hands, while he has a briefcase. Then, when they are in the car, Dawn has the puppy back with her.
When Billy Ward is interviewing Holmes, there is a scene leading into a flashback in which Holmes is shown with a freshly-lit cigarette. After the flashback, Holmes is shown with an unlit cigarette.
When Sally Hansen walks in on John and Dawn's "moment" in the bathroom, Dawn's panties are on even though John had just removed them or pulled them down a few seconds earlier.
When John leaves the hotel the night before the murders,he tells Dawn to lock up after him. She closes the safety lock. When John comes back early the next morning, he lets himself in.
John drives a blue Chevrolet Chevelle. However, the year of the car changes from scene to scene. When picks Dawn up from Sally Hansen's home, when he drives away, you see the car has round tail lights, characteristic of a 1971 model. In the scene when he drives to see Eddie Nash, the car has the square tail lights of a 1972 model.
In the beginning of the movie an over voice says that the Wonderland murders were the worst in L.A. since the 1968 Sharon Tate murder. The Tate murders actually happened in August of 1969.
When the take from the caper is being tallied, one of the items in the montage is labeled "Ludes", and includes an image of a plastic bag full of multi-colored pills. As no other piece of booty shown is represented as a pill, the bag must contain the "Ludes". Quaaludes were always white, chalky tablets, with the possible rare exception of boots from small time labs...
While seated at the table talking to the police, the tattoo on David Lind's right wrist has definite edges on each side. It appears to be a band-aid type covering.
When Ron is enraged with John, while at Wonderland, he picks up some sort of entertainment component (VCR, Cassette Player, etc...) and throws it through the picture window which crashes into the street below. Not only were there no cables attached to the component but the picture window was actually showing shatter marks before it flew into pieces when being hit by the component.
In every scene where Dawn (Kate Boswell) is supposed to be nude a blue bathing suit can clearly be seen.
When they were on Eddie Nash's boat, the Duran Duran song 'Girls On Film' is playing. That particular song wasn't released until July 13, 1981.
Towards the end of the movie, we are in Holmes' Chevelle driving towards the Wonderland apartment. The camera is inside the car and shows the rearview mirror was removed.
In a quick shot of the Capitol Records building near the beginning of the film, the shot is reversed since the letters at the top of the building are mirrored image.
At the beginning of the movie there is an overhead shot of Santa Monica Pier with a Ferris wheel. There was no Ferris wheel on the pier in 1981.
In the beginning of the movie a character is seen using a "brick" mobile phone. The first mobile phone (the Motorola DynaTAC 8000X) was brought on the market in 1983 and therefore such a phone couldn't be in use in 1981.
Right after the opening credits of the movie when John pulls up to the wonderland house, on the right side, you can spot a spanking new Volvo S80 in a driveway of one of the houses next door.
When John returns to Dawn he sits down on the bed with a six-pack of Budweiser. The cans are of contemporary type and not the straight cylindrical type of the 1980s.
The Chevrolet Caprice sedan that John Holmes was transported in to the hotel had the flush headlamps and the third brake light, making it a 1986 model.
During a television news clip about the murders, the reporter says the Wonderland Murders is the most heinous since the Tate-Labianca murders in 1968. The murders took place in 1969.