Plot hole: They found seminal fluid left in Caroline Polhemus. Why didn't they subject it to DNA testing, which would have been a powerful indicator of Sabich's guilt? Fertility (or otherwise) has nothing to do with it - as well as non-motile sperm (which contain DNA anyway) the seminal fluid would contain discarded skin and blood calls in abundance. DNA testing was first used in a criminal case in 1985 and was in fairly common use by 1988.
Presumed Innocent (1990)
1 plot hole
Directed by: Alan J. Pakula
Starring: Harrison Ford, Brian Dennehy, Bonnie Bedelia, Greta Scacchi, Raul Julia
Continuity mistake: When the reporters surround Harrison Ford, there are no tapes in the tape recorders.
Barbara Sabich: You're still in love with her.
Rusty Sabich: It was never love.
Barbara Sabich: Then what was it?
Rusty Sabich: It was never love.