Fatal

Deadly or mortal; destructive; devastating.

A fatal error in legal procedure is one that is of such a substantial nature as to harm unjustly the person who complains about it. It is synonymous with reversible error, which, in appellate practice, warrants the reversal of the judgment before the appellate court for review. A fatal error can warrant a new trial.

A fatal injury is one that results in death. It is distinguished from a disability in accident and disability insurance policies, which includes those injuries that prevent the insured from doing his or her regular job but do not result in his or her death.