Is the emotional aspect of our judicial system a positive thing?

Our legal system does not have a fixed punishment for every crime, the sentencing is left up to the judge (within limits). Similarly, the personal feelings of a jury are responsible for declaring someone guilty or innocent. This allows for more flexibility and for responding to each case individually, however, it also means that someone may get a harsher punishment because, say, the judge hasn’t had his morning coffee yet. It also allows juries to be swayed by a skillful lawyer through emotional appeal, and means that juries can be stacked with people biased for or against the defendant.