Whether defendant should have retreated was a critical part of certain offenses charged in this case. Jurors heard the State press the point at trial; they also heard conflicting accounts of who the “initial aggressor” was and whether the apartment was defendant’s “dwelling.” But the jury received no direction as to how those disputed facts related to -- or had the potential to negate -- the duty to retreat in this case. Under the circumstances, the failure to give the jury guidance on the castle doctrine was clearly capable of producing an unjust result. It was therefore plain error not to instruct the jury on the issue.