Statistics can help provide concrete examples of a larger trend, give the basis for an important chart or graph, or make theoretical arguments tangible.
There are two main branches of statistics:
Be aware of bias in statistics! Numbers can be manipulated, and charts and graphs can be arranged to give a certain impression. Always double-check your facts!
If you're looking for national crime statistics, these are some places to start your research. Consider visiting your state or city websites to look for more specific information.