@yenny47, you perfectly right. Human Rights groups are trying to see if governments can abolished the death penalty.
I think the idea of life imprisonment is to make sure an innocent person is not sentenced to death. During this period in my country, you can still appeal for the case to be relook into.
You never know, the accused or condemned could be in innocent and the judgment is change. Most cases in my country have succeeded in changing the outcome and having a more reduce and relax judgment.