PORTLAND – A judge declared a mistrial Tuesday in a civil case focusing on car seat safety that pit a Naples woman against the world’s largest car manufacturer.

After four days of deliberations that followed nearly three weeks of complex testimony, Cumberland County Superior Court jurors reported they were hopelessly deadlocked in a 4-4 split.

The judge said the trial will be rescheduled and a new jury selected later this year.

The plaintiff, Maria Allen, sued for injuries she received in an accident four years ago when her 1994 Chevrolet Lumina spun off an icy road in Poland and struck a boulder. The back of her seat collapsed from the impact, and Allen was thrown backward, hitting her head on a metal door.

Allen suffered brain injury and a skull fracture and was hospitalized for three weeks, spending some of that time in a coma. Her lawyer claimed that the mother of two would not have been injured so seriously if her seat back had not collapsed.

But the defendant, General Motors, maintained that the seat did what it was supposed to do, and that Allen’s lap belt and an armrest kept her in the front of the car, saving her life.

Evidence presented during the trial includes 97 poster-size photo blowups, 42 boxes of documents, half a dozen sample automobile seats and a fiberglass boulder. Jurors witnessed a dizzying array of computer projectors and video screens, illustrating mountains of technical testimony.