hniques to detect the presence of
substances in the victim, in the suspected criminal, or at the crime scene. For example, in
determining whether alcohol was involved in a crime, the amount of alcohol in the blood can be
measured in two ways. One is to measure the amount of alcohol exhaled in the breath of an
individual, which reveals the concentration of alcohol in the person’s blood. Recent advances
in technology have produced alcohol breath-testing instruments so accurate that their results
are evidential (capable of providing evidence in court). Blood-alcohol level can also be
determined by actual blood tests, usually through gas chromatography.
In this method, the
blood sample is vaporized by high temperature, and the gas is then sent through a column that
separates the various chemical compounds present in the blood. Gas chromatography permits
the detection not only of alcohol but also of other drugs, such as barbiturates, cocaine,
amphetamines, and heroin.1
The single greatest cause of accidents in the United States is the automobile. In 1913 the
American industrialist Henry Ford introduced assembly-line techniques in the manufacture of
motor vehicles. The subsequent increase in the number of automobiles in use was huge and
led to a great rise in the motor-vehicle accident rate. In 1991 in the U.
S., automobile accidents
were responsible for about 49.4 percent of all accidental deaths, as compared with accidents
in the home (about 23.3 percent); accidents in public places, including railroads and airplanes
(about 20.5 percent); and work-related accidents (about 11.3 percent).
The second greatest
cause of accidental deaths is falls, which account for some 13.9 percent of all fatalities.
Accidental deaths reached a high of 110,000 in 1936, with a death rate of 85.9 per 100,000. In
1991 the total was estimated at 88,000, with a death rate of 34.9 per 100,000; this was the
lowest accidental death toll since 1924 (85,600).