A Killer Among Us (1990)

"She's a juror on a murder trial... but the real killer may be sitting beside her."

Theresa is one of the twelve jurors who have to decide about a case of assassination. She believes very strongly in the innocence of the young man, but can't convince the others. During the discussions, she realizes that one member of the jury knows details that he couldn't know from the trial alone. Since no one believes her suspicions, she investigates on her own.