The Public Safety Officers Benefits Act, (42 USC 3796, Public Law 94-430) became law on September 29, 1976. The legislation provided for a $50,000 death benefit for fire fighters (paid and volunteer) and law enforcement officers that died in the line-of-duty (emergency or non-emergency) from a traumatic injury. On December 15, 2003 the Act was amended to cover deaths from heart attack and stroke occurring in the line-of-duty. The Act does not cover deaths resulting from occupational illness or pulmonary disease unless a traumatic injury is a substantial factor to the death.

http://www.iaff.org/safe/content/LODD/facts.html