Every month, law enforcement agencies report the number of known index crimes in their jurisdiction to the FBI. This mainly includes crimes reported to the police by the general public, but may also include crimes that police officers discover, and known through other sources. Law enforcement agencies also report the number of criminal cases cleared. For reporting purposes, criminal offenses are divided into two major groups: Part I and Part II offenses.
In Part I Offenses, the UCR categorizes reported incidents in two categories: Violent and Property Crimes. Aggravated assault, forcible rape, murder, and robbery are classified as violent while arson, burglary, larceny-theft, and motor vehicle theft are classified as property crimes. Collectively known as Index Crimes, these crimes are considered quite serious in nature, tend to be reported more reliably than others, and are reported directly to the police.
In Part II Offenses, the following categories are tracked: simple assault, quality of life offenses, forgery and counterfeiting, disorderly conduct, driving under the influence, drug offenses, fraud, gambling, liquor offenses, offenses against the family, prostitution, sex offenses, stolen property, criminal mischief, weapons offenses, and all other offense classifications.