Solve crimes by research and investigation. The goal of sentenced is to catch each criminal and pass judgements as best as possible; But be careful the result of your judgement will have a positive or negative effect on the convict, and on the victim at the end of each case.
The goal of sentenced is to have a positive ending after each case. You are the police, the investigator, and the judge. This is why you should handle each case with care. So if your not getting passing scores after each case try a different judgement on criminals.