crime's rate,
"crime rate" or "rate of crimes" sound better
Some people claim that there should be a pre- determined punishment for each crime
While others believe that punishmentsrules should be flexible and adjustable and should dependdepends on the situation that the subject was in and the purpose behind itthem .
Since law is one of the fundamental bases of a country that introduces discipline and stability to that countrysocial system , it should be fixed in order to be taken serious by everybody .
Well, I feel you need to have two things in mind when you do these practice essays ; Keep your writing aligned with the prompt. I think the following point is slightly out of topic;
In particular, murder is murder, no matter who has committed the crime or why, he should be punished according to the law.
--------- your prompt is about fixed and flexibility of punishment and you need to align this point with that aspect.
Second, follow the desired structure for this task.... You need to have specific examples for your reasons, which I don't find in your body paras.