When Jerry, Wade, and Stan are standing outside of the Embers, you can see I-394 over their shoulders. An overhead sign shows an HOV (High Occupancy Vehicle, or carpool) lane. Minnesota introduced HOV lanes in 1991.
The irate customer says he was paying "Ninteen Five for that car!". The MSRP for a loaded brand new 1987 Cutlass Cierra was $12,357 which the customer would have seen on the window sticker and far below his original quote.
During the parking garage sequence, the neon clock at Minneapolis City Hall (visible in some shots) shows a very different time from when the money was supposed to be exchanged. According to the same clock, nearly an hour elapses between Carl's departure and Jerry's arrival.
As Jerry and Jean tell Scotty they don't want him playing hockey, Wade calls Jerry to set up the meeting the next day. When Jean answers the phone, the time on the microwave is 10:44. When she hands the phone to Jerry, it's 7:43. When he turns his back, it's 11:05.
When Jerry drives the car and trailer into the parking lot, the only light is from the street lamps. When the camera moves from Jerry to some guys playing pool, natural light or daylight is coming in through the window.
In the opening scene where Jerry is towing the Ciera along the snow-covered roads, both cars are understandably covered with road grime, ice and salt. Later, when he pulls into the King of Clubs for the meeting, both cars are perfectly clean.
Marge asks Shep, "You do reside there at 1425 Fremont Terrace?" This address does not exist anywhere in the United States. The credits at the beginning said specifically that the movie was based on a true story.
When the kidnappers first enter Minneapolis, they are driving northbound on 35W, which means they're approaching from the south. Brainerd is north of the Twin Cities, so they should be approaching from the north.
In Brainerd, when Officer Olson interviews Mr. Mohra about the guy "going crazy at the lake," they each refer to lakes that are nowhere near Brainerd. Officer Olson asks if it's White Bear Lake, about 130 miles southeast of Brainerd. Mr. Mohra tells him it was Moose Lake. Minnesota has more than 1 Moose Lake, but the closest one is in adjacent Cass County, which is outside of the Brainerd Police department's jurisdiction. The error is repeated later, when Marge Gunderson says she is on patrol around Moose Lake.
During the investigation of the roadside shooting, Marge and her police colleague's uniforms display the American flag incorrectly on their right shoulders. The field of stars is on the left side of the flag, when it should correctly be on the right of the flag.
Jean Lundegaard dials 911 from a phone in the upstairs bathroom. A few seconds later, the phone is disconnected. While most current 911 systems could automatically identify the address, that was not the case in 1987. The dispatcher might not have been able to take any further action.
In Ludegaard's first plan to raise money, he asks Wade for seed money for a $750,000 parking lot project. Wade refuses to give him the money, but offers him a 10% finder's fee. If he took the finder's fee, he would have had $75,000 instead of the $40,000 he would have had from his second plan of splitting the $80,000 ransom with the kidnappers. However, the ransom demand was $1 million; Jerry only told the kidnappers it was $40,000.
When the patrolman approaches the kidnappers' car at night on the highway, he carries the flashlight in his left hand, and his gun and holster are on his left hip, but when he arrives at the car window, he has the flashlight in his right hand, and the gun and holster are on his right hip. This is not a goof because when the patrolman is approaching the car it's being filmed through the car's side mirror.
The state trooper turns on the flashing light on the police car way before it gets close to the kidnappers' Cierra. It means that he could not have noticed that the Cierra had dealer plates on it at such distance, at night.
When Gaear Grimsrud does a 180 degree burnout to chase the passersby who saw the dead trooper, the Tan Ciera is spinning its rear wheels, as this maneuver cannot be done with a front-wheel drive vehicle. Later, in the snowy airport parking lot, the front wheels of the Ciera can clearly be seen spinning.