Your assertion that the death penalty does not act as a deterrent is refuted by a large number of actual experts, large studies, and volumes of facts, here is just one example:
The Death Penalty as a Deterrent - Confirmed - Seven Recent Studies
Dudley Sharp, Justice Matters, updated 11/12/04
CONTACT information for all of the study authors is within the footnotes
"The results are boldly clear: executions deter murders and murder rates increase substantially during moratoriums."
(2003) Emory University Economics Department Chairman Hashem Dezhbakhsh and Emory Professors Paul Rubin and Joanna Shepherd state that "our results suggest that capital punishment has a strong deterrent effect. An increase in any of the probabilities -- arrest, sentencing or execution -- tends to reduce the crime rate. In particular, each execution results, on average, in eighteen fewer murders -- with a margin of error of plus or minus 10." (1) Their data base used nationwide data from 3,054 US counties from 1977-1996.
(2003) University of Colorado (Denver) Economics Department Chairman Naci Mocan and Graduate Assistant R. Kaj Gottings found "a statistically significant relationship between executions, pardons and homicide. Specifically each additional execution reduces homicides by 5 to 6, and three additional pardons (commutations) generate 1 to 1.5 additional murders." Their "data set contains detailed information on the entire 6,143 death sentences between 1977 and 1997. (2)
(2001) University of Houston Professors Dale Cloninger and Roberto Marchesini, found that death penalty moratoriums contribute to more homicides. They found: "The (Texas) execution hiatus (in 1996), therefore, appears to have spared few, if any, condemned prisoners while the citizens of Texas experienced a net 90 (to as many as 150) additional innocent lives lost to homicide. Politicians contemplating moratoriums may wish to consider the possibility that a seemingly innocuous moratorium on executions could very well come at a heavy cost." (3)
(2001) SUNY (Buffalo) Professor Liu finds that legalizing the death penalty not only adds capital punishment as a deterrent but also increases the marginal productivity of other deterrence measures in reducing murder rates. "Abolishing the death penalty not only gets rid of a valuable deterrent, it also decreases the deterrent effect of other punishments." "The deterrent effects of the certainty and severity of punishments on murder are greater in retentionist (death penalty) states than in abolition (non death penalty) states." (4)
(2003) Clemson U. Professor Shepherd found that each execution results, on average, in five fewer murders. Longer waits on death row reduce the deterrent effect. Therefore, recent legislation to shorten the time prior to execution should increase deterrence and thus save more innocent lives. Moratoriums and other delays should put more innocents at risk. In addition, capital punishment deters all kinds of murders, including crimes of passion and murders by intimates. Murders of both blacks and whites decrease after executions. (5)
(2003) FCC economist Dr. Paul Zimmerman finds: "Specifically, it is estimated that each state execution deters somewhere between 3 and 25 murders per year (14 being the average). Assuming that the value of human life is approximately $5 million {i.e. the average of the range estimates provided by Viscussi (1993)}, our estimates imply that society avoids losing approximately $70 million per year on average at the current rate of execution all else equal." The study used state level data from 1978 to 1997 for all 50 states (excluding Washington D.C.). (6)
(2003) Emory University Economics Department Chairman Hashem Dezhbakhsh and Clemson U. Professor Shepherd found that "The results are boldly clear: executions deter murders and murder rates increase substantially during moratoriums. The results are consistent across before-and-after comparisons and regressions regardless of the data's aggregation level, the time period, or the specific variable to measure executions." (7)
The findings reflect reason, common sense and history.
"According to the standard economic model of crime, a rational offender would respond to perceived costs and benefits of committing crime." "Capital punishment is particularly significant in this context, because it represents a very high cost for committing murder (loss of life). Thus, the presence of capital punishment in a state, or the frequency with which it is used, should unequivocally deter homicide." Furthermore, "an increase in pardons (commutations) implies a decrease in the probability of execution, which economic theory predicts should have a positive (increase) impact on murder rates." (8)
Isaac Ehrlich (1975) provided the first systemic analysis of the relationship between capital punishment and the crime of murder along with the first empirical analysis of the deterrence hypothesis. He found that each execution deterred, on average, 8 murders. Many additional studies have found corroborating evidence supporting the deterrent effect of the death penalty -- from the United States (Ehrlich, 1977, Layson, 1985, Cloninger, 1992, Ehrlich and Liu, 1999, Dezhbakhsh et al, 2000) and Canada (Layson 1983) and the UK (Wolpin, 1978). (9)
Pubic policy makers take note. Stopping executions will sacrifice innocent lives. Reinstating capital punishment will spare more innocent lives.