Is Capital Punishment justifable?

Capital Punishment is also known as the death penalty, which means the execution of a convicted criminal as punishment for his serious crimes, eg. murder. It is often carried out in countries to punish the offender, to compensate the people which he affected and took away a person they knew and loved.
But i myself have divided opinions about this capital punishment. Is it truly necessary? I feel that capital punishment is really cruel and not at all justifable. I feel that people in the government are hypocrites on this issue. They tell us to follow the law and not to commit heinous crimes like murder etc. but they themselves do not present a good example to the public by killing the offender. Yes, this punishment might be needed to appease the victim's family or loved ones but we can think of new and better ways to punish the offender.
Why do i think that capital punishment has no effect? Look at the number of people who are still being convicted of commiting murder, kidnapping etc, since capital punishment had been implemented. It has not show signs of decreasing despite the serious punishment being meted out to convicted offenders. This shows that the capital punishment is not useful at all and should be abolished.
Many offenders before they commit their crimes, would have thought of the consequences, what will happen to them and prepared themselves beforehand. Thus they are not concerned by the death penalty, and would go ahead with whatever they plan to do. The death penalty insteads in another light, allows them to not face the consequences of their actions and offers them an easy way out.
I feel that we should remove the capital punishment and instead replace it with a more reasonable and punishing one. We could lock them up in jail for life and make the offender do things to make up for their actions to people involved. In this way, they would probably feel how their actions had been foolish and how it had affected other people and make them guilty. This would probably be the best deterance. When people know that when they commit crimes they cannot escape from it and have to repay, it would probably make them think twice. What do you say?