Micro GPS tracking devices inhaled into the lungs of everyone on earth, three different units. One measuring body temperature and heart rate, one sending this information to a central collection unit, and one tracking placement on the globe.
No one could die without the knowledge of who was around that person at that time; no crime could be committed without the knowledge of the persons in the area at the time. Anyone suffering a heart event could have emergency personal sent without the need of a phone call.
The placement of the chips in the lungs would insure they could not be removed without the death of the recipient. Then everyone could feel secure in a new form of slavery that could not insure a person of not being murdered, but could insure that the murderer would be found and punished.