According to the Department of Justice Federal Bureau of Investigation's Uniform Crime Reporting Handbook (p. 131-139) there is no indication of a minimum length of a crime report narrative. What the handbook strongly emphasizes on, however, is on the fact of being concise and to the point.
A police report narrative is the re-stating of the information that is required in the Basic Factual Information box where the agent lists down all the data regarding the crime including:
- date, time, and place where event took place
- description of suspects
- description of the event itself.
- witness testimony
In an optimal scenario a seasoned investigator would have a customized header for the preliminary information to be recorded. This is because each individual takes notes in different ways. However, during the narrative all of the information recorded has to be re-hashed and explained in a manner that involves the agent and demonstrates active participation.
Therefore, a narrative will include the points stated at the beginning, the manner in which the agent approached the witnesses, what was said, and any additional information that the agent considers to be salient. It is about conciseness and about adding the information that was gathered. The length cannot be minimalistic unless it presents all the points to be discussed. It also should not be so extensive that it misses the vital points. Number of words are not at issue.