14. If no harm results from an allegedly negligent act, there is no liability. 15. An assumption of risk defense does not require that a risk be voluntarily assumed. 16. Under the "danger invites rescue" doctrine, a person who tries to rescue another individual from harm is liable for any injuries to that individual. 17. The extreme risk of an activity is a defense against imposing strict liability. 18. Criminal law spells out the duties that exist between persons or between citizens and their governments. 19. A criminal case must be proved beyond a reasonable doubt.