There will be many who argue that capital punishment does decrease murder rates. They would suggest that the use of capital punishment makes a statement to all those who would violate the social contract of existence that there will be definite and powerful consequences to their actions. They will also argue that the risk of murderers being released early to simply commit the same crime again is eliminated with the effective use of capital punishment. Of course, it can be equally argued that there is no change in murder rates if the state participates in murder through capital punishment. It is in logic like this were the subtext of your question is addressed in that an equal number of people believe that there is something morally and philosophically wrong with a state that stands against murder, but then participates in capital punishment. As a measure, they would argue that to take away the life of a prisoner is the worst form of violation of their human rights.
It sounds to me like you are specifically looking to use the human rights arguement to answer your anchor question.
If that's the case, the issue of human rights is indeed debatable, so if you want to look at the arguments of the sides of the issue, the website below will give you some information worth viewing, it also has links at the bottom worth looking through.
I would also search google using "capital punishment con human rights". See what you get.
Of course, there is no way to answer this question objectively. No answer can be anything more than an opinion.
You can argue that it is not acceptable. You can say that society should not be allowed to determine who deserves to die and who does not. You can say that kind of judgement should be left to God, for example. Or you can say that people are just not able to make this judgement in any kind of fair manner.
But you can argue that it is acceptable. You can say that people who commit certain crimes have acted in such an inhuman way that they no longer deserve to be treated as human beings.
Human beings have a right to life, but the issue of Capital Punishment being used as a form of consequence for murder is a difficult decision.
Capital punishment does not really work as a deterrent to prevent murder. The majority of murders are committed during emotionally charged moments and occur between people who are familiar with one another. During an emotionally charged moment impulse control is less likely to kick in and that is why the person is not able to process the idea that "if I kill this person I will be put to death." Therefore, the fear of one’s own death is not present at the time.
Another problem in using the death penalty to deter murder is that many murders are committed by someone under the influence of drugs or alcohol. The person's state of mind is less likely to be considering consequences for his actions as it would be reacting to the stimulus in the environment and situation that he is in at the time of the murder.
In the case of serial killers, the drive that motivates them is so deeply innate that consequences for their actions are not a deterrent.
Capital punishment is not an effective means for preventing murder, but it is an effective means of punishment for murder and serves to eliminate society from serial killers such as Ted Bundy. Ted Bundy while incarcerated had managed to escape and kill more women during his escape. His death ended his reign of terror and the risk of harm to others.
(I am quoting facts that I have learned through sociology classes and do not state an opinion for nor against capital punishment.)