Evaluation of Argument Against Parfits Reductionism

HI, below is an argument against Parfit's reductionsim theory. I am not sure if I covered it good enough. And if it is a good, valid rgument, what can I do to better this argument in light of objections to Parfits argument? Any additional information would be great help, and if there are any errors please let me know. Is there any other possible objections to Parfit's argument?

PARFIT'S REDUCTIONISM

Derek Parfit upholds the Reductionism theory of personal identity believing that a person is nothing over and above his brain and body, and certain deeds and thoughts. He maintains that with the passage of time, man's thinking changes which results in the creation of a new identity and therefore man at present may lack connection with the man he was in the past.
This argument fails to take into account deliberation concerning morality and rationality. If a person is no longer the person he was say ten years ago, does it mean that the crime he committed in the past wasn't exactly done by him. In other words, if a person needs to change his views on identity, he will probably have to change his views on morality too.
But this can have dangerous repercussions. Suppose Tom kills Sam at the age of 25, however he manages to escape imprisonment and roams around freely for ten years. Then suddenly evidence surfaces proving his involvement and he is sentenced to death. Would we say that the Tom who killed Sam ten years ago is not the same Tom anymore and thus should not be arrested or sentenced? A person at 35 may not have same beliefs and thoughts that he had at 25 yet he is essentially the same man because of his personal identity. This means that the only thing that a person never gets rid of is his consistent and concrete personal identity, which is the one strong link between present-him and 'past-him'.