In countries where the death penalty is banned, murder rate is what

compared to US?

and at the Death Penalty Information Center.
http://www.deathpenaltyinfo.org/article.php?scid=12&did=168

From AmnestyInternational:

8. Effect of abolition on crime rates
Reviewing the evidence on the relation between changes in the use of the death penalty and homicide rates, a study conducted for the United Nations in 1988 and updated in 2002 stated: "The fact that the statistics continue to point in the same direction is persuasive evidence that countries need not fear sudden and serious changes in the curve of crime if they reduce their reliance upon the death penalty".

Recent crime figures from abolitionist countries fail to show that abolition has harmful effects. In Canada, for example, the homicide rate per 100,000 population fell from a peak of 3.09 in 1975, the year before the abolition of the death penalty for murder, to 2.41 in 1980, and since then it has declined further. In 2003, 27 years after abolition, the homicide rate was 1.73 per 100,000 population, 44 per cent lower than in 1975 and the lowest rate in three decades.

(Reference: Roger Hood, The Death Penalty: A World-wide Perspective, Oxford, Clarendon Press, third edition, 2002, p. 214)

http://web.amnesty.org/pages/deathpenalty-facts-eng