A murder mystery by the numbers
This is a different kind of murder mystery.
For years, social scientists have tried to determine whether the death
penalty has a deterrent effect. Put another way, does the death penalty
In 1967, sociologist Thorsten Sellin found no significant impact when he
studied murder rates in adjacent states with differing approaches to
The next year, Nobel Prize economist Gary Becker developed a theory
supporting the deterrent value of the death penalty, and eight years later
one of his students published a study based on national statistics
purporting to show that each execution saved 8 lives.
The controversy led to a study commissioned by the National Academy of
Sciences that found evidence of deterrence to be unconvincing.
More recent studies have reached conclusions all over the map. A national
study in 2005 found "profound uncertainty" on the question and even
suggested that executions might slightly increase the murder rate
(possibly through a cultural "brutalization"). Another study that year
suggested that each execution saves 150 lives.
All these studies are noted in a peer-reviewed article about to come out
in Criminology, the journal of the American Society of Criminology. The
study was conducted by Duke University Sociologist Kenneth C. Land, Sam
Houston State University criminologist Raymond Teske Jr. and one of Land's
graduate students, Hui Zheng.
Land is a prominent specialist on research methodology. He earned his
doctorate at the University of Texas and chaired Duke's sociology
department from 1986 to 1997.
After reviewing earlier studies, these authors came to the conclusion that
the death penalty is used too sporadically and inconsistently around the
nation for studies on national data to accurately measure its effect on
They decided to focus their study by taking advantage of Texas' gift to
social science, what they call "an orgy of executions in Texas beginning
in 1994," during which time the state provided more than 1/3 of the
To measure the impact of executions, the authors looked at 2 distinct
The 1st was from 1980 through 1993, when for a variety of legal reasons,
executions were relatively infrequent and uncertain. In those years there
were about 8 executions a year, and about 5 convicts a year removed from
death row for various reasons.
A series of legal decisions and changes in law designed to speed up
executions led to a dramatic change after 1994. From then through 2005,
the number of annual executions tripled and the rate of prisoners being
removed from death row plummeted.
Using sophisticated statistical models, the researchers tested the impact
of the larger number of executions.
They found that many earlier studies had vastly overestimated the effect,
but the number of murders did go down in the short-term aftermath of
Based on 2 different statistical models, they found the effect in the
months after each execution to be a reduction of between 0.5 to 2.5
That may not sound like much, but as the authors note, "even the estimated
.5 deterrent per execution yields an estimated reduction in the expected
numbers of monthly homicides of 5 to 10 during the subsequent 12 months,
which is substantial."
I'm sure this isn't the last word on the issue. That's no mystery. Here's
This study and previous ones show no correlation between the amount of
publicity executions receive and their deterrent effect.
"We have no theory on that," Teske said on Friday. After a few more
questions, he said, "I hear your frustration. If I wasn't working with one
of the top guys in the nation, my confidence would be shaken."
One other mystery: The study shows, as other studies have, more impact on
the kinds of murders that don't qualify for the death penalty than on
those that do.
(source: Commentary, Rick Casey, Houston Chronicle)