Even after the facts are determined, no decision can be reached without de- termining what the law is. The law varies from place to place and from time to time, so we have to know what the law is at the right time and place. This is determined mainly by looking at the legal institutions that actually exist. In our legal system, there are three main sources of the law: statutes, the Constitution, and precedents.
STATUTES. Roughly, statutes are general rules of law passed by legisla- tures. Statutes are made at various levels (federal, state, and local), and they cover various subjects, including crimes as well as property, contracts, and other areas of civil law. There are also statutes governing the procedures and kinds of evidence that can be presented in court.
When a general statute is applied to a particular case, the legal argument is often primarily deductive. For example, Sally drove ninety-five miles per hour in front of Hanover High School at 4 PM on a school day. It is illegal to drive over fifteen mph in front of any school at 4 PM on a school day. Therefore, Sally’s driving was illegal. Of course, there are lots of suppressed premises, such as that ninety-five mph is over fifteen mph. Other assumptions are trick- ier: Sally might not be found guilty if she had an excuse or justification, such as that a terrorist held a gun to her head. Still, it is often obvious that Sally had no excuse or justification. If we add this claim as a premise, then, with a little fid- dling, the legal argument against Sally can be made deductively sound.