Police Commissioner William J. Bratton lists the following guidelines on his blog. There is some doubt among scholars that Sir Robert Peel actually enunciated any of his nine principles himself — some researchers say they were formulated in 1829 by the two first commissioners of London’s Metropolitan Police Department.

PRINCIPLE 1 “The basic mission for which the police exist is to prevent crime and disorder.”

PRINCIPLE 2 “The ability of the police to perform their duties is dependent upon public approval of police actions.”

PRINCIPLE 3 “Police must secure the willing cooperation of the public in voluntary observance of the law to be able to secure and maintain the respect of the public.”

PRINCIPLE 4 “The degree of cooperation of the public that can be secured diminishes proportionately to the necessity of the use of physical force.”