Continuity mistake: The bottle of Peach Schnapps that Trip (Josh Hartnett) brings to the dance is alternately full and half empty during the scene. When Trip pulls it out, it is new and unopened. He hands it to Lux to drink, at which time it is nearly empty. He then drinks from it, and it is about half-full. He next hands it to the other couple, at which time the bottle is nearly full again. (00:57:56)
Continuity mistake: At Tripp's first visits to Lux's family, when he gets up to leave, Lux gets up also. She is clearly wearing light blue colored jeans. When she walks Tripp to the door, she's wearing black colored jeans or black sweatpants.
Continuity mistake: During the scene when Peter Sisten is eating dinner with the Lisbons, Cecilia is not wearing her bandages on her arms. In the scenes immediately before (Cecilia in the psychiatrist's office) and after (the girls lounging on the front yard) Cecilia has the bandages on.
Factual error: In the scene where the boys are driving to (or from) the dance, while driving down the street, you can clearly see a 1988-1991 Honda Civic hatchback in a driveway. Obviously this car was overlooked since this movie was set in the 1970's.
Continuity mistake: After Cecelia's tree is cut down, there is a shot of the house, and the tree is back upright again.
Continuity mistake: When the Lisbon girls are surrounding the tree stopping the guy from cutting it down, between shots Therese's scarf changes position during shots. (01:12:00)
Other mistake: The news reporter who comes to interview the family after Cecilia's death tells Mrs. Lisbon she's from Channel 2, when in fact we can see from her news report moments later a Channel 8 logo on the screen (and on her truck).
Visible crew/equipment: During football practice, right after Kevin Head offers Trip three joints to take one of the Lisbon girls to homecoming, the shadow of the boom pole is visible on Trip's head and back.
Factual error: A medical examiner or coroner (or other physician) typically determines cause of death, so unless Father Moody had a medical degree, his statement to Mr. And Mrs. Lisbon - he "listed Cecilia's death as an accident" - would not be official. It also isn't revealed exactly where Father Moody made such a listing.