Certain forms of police lying or deception are an accepted part of the police officer's working environment. This type of lying or deception is deemed by police managers to be an acceptable means of enforcing various laws. Such deception is part of undercover policing, "sting" operations, the securing of confessions, protection of the innocent, protection of the image of the department, and the calming of the public in crisis situations. A second category of police lies involves those viewed as "necessary evil." These stem from police beliefs that certain suspects are guilty, although there may not be sufficient valid evidence to obtain a guilty verdict in court. Police may then engage in lying and deception in an effort to bolster the appearance of guilt. Another category of police lying is for the purpose of promoting illegitimate goals, so as to protect an officer from organizational discipline or from civil or criminal liability. The effects of all categories of police lying, whether or not the police organization accepts or tolerates them, is to undermine the credibility of the police organization. If the public believes that it is common practice for police to lie and deceive to achieve their goals, then the public's trust in a fair and forthright administration of justice deteriorates. Police should establish a code of ethics and values that is a true statement of the behavioral standards toward which the organization aspires. Policy, directives, training, and supervision should then provide consistent and unambiguous support for the behavior specified in the code of ethics. 21 references and 5 study questions