A person is negligent, or acts negligently, when that person 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 that failure constitutes a substantial deviation from the standard of care that a reasonable person would exercise in the situation.
(ILCS Ch. 720, Act 5, § 4-7) (1999 Code, § 130.05)