Amends the Unified Code of Corrections. Provides that the court shall sentence the defendant to a term of natural life imprisonment for first degree murder if the defendant, at the time of the commission of the murder, had attained the age of 18, and is found guilty of the first degree murder of a child under the age of 5 who is determined by the court, upon testimony of a physician, to have died from abusive head trauma caused by the defendant. Provides that "abusive head trauma" includes shaken baby syndrome. Defines "abusive head trauma" and shaken baby syndrome".