When Aileen pushes Selby back into the Grand Am, a large tattoo is on the small of Selby's back. Earlier, when Aileen took off Selby's shirt in bed, Selby had no back tattoo.
After Aileen kills the first john, she stands over his body with her underwear around her knees. The shot switches to the dead man on the ground, then back to Aileen with her underwear and pants all the way up.
When Selby is cutting off her cast in the motel room, the bathtub has a shower curtain. When Aileen is showering after killing her second victim, the shower has a glass door.
When Lee and Selby are in the red car, and Lee is talking about her childhood, Lee's cigarette alternates from short to long and back between shots.
When Aileen tells Selby about her family and childhood, they are riding in a red 1993 Grand Am. When the car crashes, it is a 1988 Grand Am.
Throughout the film a huge cast is on Selby's arm, but her shirts are tight in the arms. Her cast would never fit through the sleeves.
When Selby calls her father from her aunt's house, the cordless phone's antenna is retracted. In the 1980s, cordless phones only worked if the antenna was fully extended.
The postscript says Aileen Wuornos was executed after 12 years on Florida's Death Row. She was arrested January 9, 1991, sentenced to death January 31, 1992, and executed October 9, 2002. Starting from the date she was arrested, it adds up to 11 years, 9 months.
A revolver can hold more than 6 bullets. Most large frame .22 caliber revolvers, the type Aileen used, can hold 9 bullets.
When Lee talks to Selby on the phone, her brown contact lens move, revealing Charlize Theron's green eyes.
When Aileen meets Selby in the bar, a girl in the background gets taller as she walks between them. A platform was placed under the floor so Christina Ricci didn't look so short next to Charlize Theron.
The amusement park in the film is called "Fun World". However, "Fun Spot" logos are clearly visible on walls and the roller coaster.
When Aileen and Selby are about to kiss at the roller rink, Selby's cast moves to her left arm in one shot.
When Selby and Aileen sit against the wall outside the bus station, Selby's boots are brand new, with no dirt on the bottom.
At the beginning of the film, Lee sits under an overpass of a major Interstate. Many of the passing cars are from the early 2000s, not the 1980s.
When Lee applies for a job, the application is briefly visible. One line says "e-mail address". The Internet existed in 1990, but e-mail wasn't available to the masses until later in the decade.
An early shot shows The Daytona Beach pedestrian walkway bridge, which was completed in 2002.
In the end of the film, when Aileen is sitting under the overpass along the interstate, a late model LYNX bus is visible. LYNX was called Tri-County Transit until 1992. In 1994, it became the Central Florida Regional Transportation Authority.
Aileen and Selby crash a mid 1990s Grand Am.
Selby moves into the motel room, and Aileen tells her she quit hooking. When Aileen sits in the chair, an unseen crew member moves, casting a large shadow across the set.
Lee is interviewed to be a legal secretary, even though she doesn't have a resume. How would a law office even give her an interview without a resume?
When Aileen fills out a job application, she writes her name as "Wournos, Lee C." The correct spelling is "Wuornos."