Other mistake: Right after Heather Duke and Heather McNamara drop in on Veronica and Betty Finn playing croquet, Veronica talks to her parents about the suicides. She still has a croquet mallet in her hand, so little time can have passed. Heather Duke rushes in with a shopping bag, and tells Veronica that while at the mall they heard about Martha Dumptruck's suicide attempt. But Heather Duke had just left Veronica's house - there wasn't enough time for these events to happen.
Heathers (1988)
1 other mistake - chronological order
Directed by: Michael Lehmann
Starring: Christian Slater, Winona Ryder, Shannen Doherty, Lisanne Falk
Revealing mistake: When they show Heather Chandler in her casket in the funeral scene and everyone is praying, she's clearly breathing.
Pauline Fleming: I think it's a good opportunity to share the... feelings that this suicide has spurred in all of us. Now, who would like to begin?
Female Stoner: I heard it was really gnarly. She sucked down a bowl of multi-purpose deodorizing disinfectant, and then smash.
Pauline Fleming: Now Tracey, let's not rehash the coroner's report. Let's talk emotions.
Trivia: Veronica Sawyer and Betty Finn's names are a combination of the girls from the 'Archie' comic books, and Mark Twain's characters Tom and Huckleberry.
Question: Why did JD expect anyone to believe his plan for the bomb at school - that all of the students signed a mass suicide note? Nobody would think that so many people, with different personalities and interests, agreed to die together. He later tells Veronica, "Pretend I did blow up the school, all the schools" - implying that he wanted to do this again. He might be crazy, but he was careful in how he executed the murders of Heather, Kurt, and Ram. Why the ridiculous bomb plan?
Answer: The students didn't know they were signing a "mass suicide" pact. They thought it was a petition to win a free concert from a popular band. JD covered the suicide wording on the paper with a sticker that made it look like a contest entry. He pulls off the sticker and reads the real message after he finds Veronica hanging in her room.
That was not the question. It's a question of why JD thinks anyone will believe the note, after all the students are dead. Has nothing to do with the students knowing what they were signing.
Answer: He doesn't care if anyone believes it or not; he is trying to make a statement about society and that no matter how we see ourselves in life, we are all the same when we're dead.