Murder rates, like other crime rates, have been falling in the United States for nearly a decade. But the fall in the murder rate cannot just be chalked up to better police work, according to a Washington Post story reporting on a new study in the journal Homicide Studies. A lot of the credit has to go to advances in medical science.

Researchers at Harvard University and the University of Massachusetts, analyzing 40 years of criminal assault and murder statistics, found that deaths in the United States from criminal assaults dropped almost 70 percent over the past 40 years. In 1960, there were 9,110 homicides and 154,320 aggravated assaults, resulting in 5.1 homicides per 100,000 people and 86.1 assaults per 100,000. That means that 5.6 percent of assaults ended in murder.

In 1999, there were 15,522 homicides, a rate of 5.7 per 100,000, and 911,740 aggravated assaults, a rate of 334.3 per 100,000. That means only 1.67 percent of the assaults ended in death.

The researchers concluded that without improvements in emergency care, the establishment of 911 services, and the spread of techniques for the rapid stabilization and transportation of trauma victims, the higher rate of assaults in the U.S. in 1999 would have more than tripled 1999's murder rate to between 45,000 and 70,000.

Of course, advances in trauma care are not just saving might-have-been murder victims, but are also improving survival rates for all kinds of injuries. For example, the U.S. Centers for Disease Control note that deaths from occupational injuries have fallen by 28 percent, from 7,343 in 1980 to 5,285 in 1997. Taking into account the swelling U.S. labor force, this means that the rate for occupational injury deaths decreased 45 percent, from 7.4 per 100,000 workers in 1980 to 4.1 per 100,000 in 1997. Of course, work place safety improvements also reduced occupational death rates, but a good bit of the credit must go to advances in medical science.

The report in Homicide Studies also raises a couple of legal and philosophical questions: (1) Are criminal assault rates a better measure of the amount of crime actually experienced by citizens, and (2) What punishment does a cold blooded would-be murderer deserve if he fails only because of medical science?