Although common-law systems make extensive use of statutes, judicial cases are regarded as the most important source of law, which gives judges an active role in developing rules. For example, the elements needed to prove the crime of murder are contained in case law rather than defined by statute. To ensure consistency, courts abide by precedents set by higher courts examining the same issue. In civil-law systems, by contrast, codes and statutes are designed to cover all eventualities and judges have a more limited role of applying the law to the case in hand. Past judgments are no more than loose guides. When it comes to court cases, judges in civil law systems tend towards being investigators, while their peers in common-law systems act as arbiters between parties that present their arguments.