I appreciate reading such a thought- full question.
Yes a murderer, does have free will. If an individual chooses to exercise free will and commit murder, then that person is subject to punishment, by criminal law and the law of God.
Each individual is responsible for their own actions. The mis-use of free will is the individuals responsibility, not God's nor society.
Therefore it is critical for everyone in the human form of life, to know what proper activities are, otherwise that individual may be living very dangerously.
If anyone with a human form of life, does not understand the difference between human activity and animal activity, then their future is indeed bleak.
The murderer is not being punished for his free will, he is subject to punishment for mis-using his free will.
Everyone has the potential to mis-use their free will, if you could not choose to something wrong, then you couldn't choose to do something right, right and wrong would have no meaning.
If God did not grant free will, then there would be no choice's, we would then indeed be puppets or robotic, programmed entities, love is unconditional, you cannot force someone to love you, if you could it would be meaningless, without that individual making a personal choice.
God is omniscient, he knows all that is happening in the past, all that is happening in the present and all that is happening in the future, within the infinite world's.
Although a person has commited murder, they can still be rectified by attoinment, certainly that individual soul will be forced to endure the same degree of suffering that they themselves have inflicted, in an equel and opposite manner. In Christian theology it is stated "The measure that you give, will be the measure that you get", or in Vedic terms, Karma or cause and effect, which is experienced over past lives and future lives.
You are responsible for your own actions, choose the right actions and make your human life successfull.
To discuss further:- Sriman Sankarshan Das Adhikari (sda@backtohome.com)