A person is negligent or acts negligently when he or she fails to be aware of a substantial and unjustifiable risk that circumstances exist or a result will follow, described by the statute defining the offense and the failure constitutes a substantial deviation from the standard care which a reasonable person would exercise in the situation.
(ILCS Chapter 720, Act 5, § 4-7) (1981 Code, § 42.04, 4-7)