There are numerous problems with this application. Unfortunately, religious doctrine does have influence in public policy. In this case it could be argued that parliament is leading the way in upholding human rights and continues to broadcast the clear message that killing is always wrong.
The extermination of the wicked is not in consonance with the eternal law. The brutalization effect has it that the rates of homicides will tend to go up because of the executions in states.
This report will explore For example, females and close relatives of the criminal are precluded from being witnesses according to Biblical law, while full-time gamblers are precluded as a matter of Rabbinical law.
There are of course many more. The possibility of executing the innocent is of serious concern, especially outside of the West.
The jury is also a factor in determining penalty.