The acquisition and organization of legally reliable evidence is the essence of the criminal investigation process. Evidence is usually obtained through the use of one or more of the three I’s of investigation: interviewing, instrumentation, and information. Information provides direction to investigation. Information about a crime may be obtained from many sources. However, people motivated by the desire to improve the community usually have only limited knowledge of crime. Investigators must often turn to another, more questionable source of information: the criminal informant.

American law enforcement agencies have long made use of informants. In the nineteenth and early twentieth centuries, detectives concentrated on identifying suspects and set about building a case from testimony of witnesses and confessions, or from actually catching offenders in the act (Lane 1967; Richardson 1970).

In time, investigators began to concentrate less on suspects and more on crimes. The shift away from suspects came because investigators began to view the collection of physical evidence as the most essential part of their job. However, an interest in the use of informants has reemerged. A major conclusion from a study of investigation methods suggested a need for both patrol officers and investigators to make greater use of informants (Eck 1983).

Using an Informant’s Information

The concept of probable cause is at the heart of American law enforcement. Of particular importance is the hearsay method for establishing probable cause most commonly used by officers relying on informants.

In Aguilar v. Texas, the Supreme Court created what became known as the two-pronged test for establishing probable cause on hearsay evidence. This test required that two things be done: (1) that the credibility of the informant be established, and (2) the reliability of the informant’s information also be established.

The establishment of an informant’s credibility was usually satisfied in one of two ways. First, if the informant made statements that led to prosecution this was generally considered proof of an informant’s reliability. This technique is particularly valuable when using informants for the first time.

Multiple use of an informant establishes a ”track record,” the second means used to demonstrate an informant’s credibility. A police officer preparing an affidavit for a warrant can cite the track record as proof that the informant has provided accurate information leading to a specified number of arrests and convictions. Demonstrating the reliability of an informant’s information, the second prong of the test, is most commonly accomplished by stating the informant’s direct knowledge of the facts.

In Spinelli v. United States, the Supreme Court approved the technique of corroboration as a means to establish probable cause. Under this concept, the Court suggested that facts, when combined in sufficient number, could establish probable cause. Thus, traditional investigative techniques such as surveillance, record checks, and neighborhood canvasses could be of value in obtaining warrants.

In 1983, the Supreme Court handed down a decision that impacted the use of informants. In Illinois v. Gates, the Court established a totality of the circumstances test to determine the existence of probable cause. In Gates, a police officer received an anonymous letter so detailed that a judge felt the information contained in the letter was adequate to establish probable cause and issued a search warrant. At no point in the letter did the informant identify himself or provide information as to his credibility, from the perspective of Aguilar. The judge inferred the informant’s credibility from the detailed information provided in the letter. The Court had eliminated the ”first prong” of the two-pronged test, that of establishing credibility of the informant. Presently, the techniques set forth in Aguilar, Spinelli, and Gates affect use of an informant’s information.

Protecting an Informant’s Identity

Investigators must make every effort to protect informants. The reasons are obvious: No one can be expected to provide information if it leads to his or her injury, death, or ostracism. Two cases have established principles that determine circumstances under which courts can compel disclosure of an informant’s identity. In a 1957 case, Roviaro v. United States, the Supreme Court held that when an informant is a material witness in a case, such as a participant, his or her identity must be revealed to the defendant. This requirement stems from the Sixth Amendment, the right of a criminal defendant to confront his accusers. Thus, if an informant is actually making drug buys, for example, this activity must be undertaken with the informant aware that he or she might have to testify in court. In a later decision, however, the Supreme Court held that where an informant, whose reliability has already been established, only provides information that establishes probable cause, the informant’s identity need not be disclosed (McCray v. Illinois).

In some states, the identity of an informant may be protected as a privileged communication between police officer and informant. Where that privilege exists, a police officer may refuse to disclose the identity of an informant who has only provided information leading to probable cause. In those states where privilege does not exist, an informant’s identity may be treated as a matter of relevancy. A prosecutor may argue that as long as the informant is not a material witness, revealing his or her identity is not relevant. The trial judge will then make an in camera determination on the need to reveal the informant’s identity.

Problems Related to the Use of Informants

By its very nature, the use of informants requires secrecy. The potential for abuse is therefore enormous. One of the most complex problems concerns to whom informants should provide information. Should they provide it only to specified police officers who will then have exclusive use of the information or should the informants’ names and their information be maintained in a master informant file?

Proponents of individual control argue that informants are developed on a personal basis. A working relationship, based on a degree of trust, facilitates the flow of information. Once the relationship has been altered by inclusion of the informant’s name in a master file, the informant’s fear of exposure may hinder the acquisition of any further information. Another argument is that once the informant’s identity is known to others it may become impossible to protect his or her identity, despite the most stringent security measures.

Arguments in support of centralized control hold that centralization reduces the potential for corruption either by police or informants. Administrative review may serve as a check on police officers engaging in corrupt and illegal acts. Centralization also makes an informant’s information available to other investigators.

Use of informants also presents problems vis-a-vis the system as a whole. The American criminal justice system is rooted in the concepts of accountability and punishment; that is, persons are to receive their just desserts for violating the law.

The ”buy-bust-flip” procedure by which informants are developed reduces the certainty of being held accountable for violating the law. The ”buy-bust-flip” technique of developing informants is well documented (Jacobson 1981; Wilson 1978). In its simplest form, the technique involves hand-to-hand purchases of drugs: the buy. The buy results in an immediate arrest, the bust. The arrestee is then given an unpleasant choice: going to prison or becoming an informant (the flip). While it could be argued that being compelled to perform in the sometimes risky role of informant is a form of punishment, it is equally likely that the person will feel it to be the more attractive option. But the threat of punishment cannot be effective as a deterrent unless it is certain. As long as law violators believe that an avenue of escape as an informant exists, there can be no certainty of punishment.

Another problem of informant use relates to the selection of a target. Investigations tend to focus on individuals and activities already known to the informant, not necessarily on the most serious offenders. Allocation of resources should be made only after careful sifting of all available information, rather than on only the idiosyncratic knowledge of an informant. The decision to investigate someone is also tied to the amount of ”buy money” available. For example, if an agency’s resources are limited, purchases will be small. The larger the budget, the larger the prize. Eventually, however, the prize becomes too expensive and the person making the last transaction becomes the target. Thus, money, not criminal activity, determines who is prosecuted.

Informant Control

The Commission on Accreditation for Law Enforcement Agencies requires that agencies seeking accreditation establish policies governing the use of informants. Although it is unrealistic to expect law enforcement agencies to develop an all-encompassing policy, it is necessary to promulgate a series of workable guidelines. The policy statement should begin with a frank declaration that informants are a valuable resource to be used. Information provided by informants will be kept in a master file, but access must be tightly controlled. The policy must state that neither the agency’s administration nor its individual members will allow informants to commit crimes, and those who do will be prosecuted. Officers must be prohibited from offering immunity without review by the prosecuting attorney. Informants must be briefed on entrapment laws and warned that they cannot present themselves as sworn or nonsworn employees of the agency. Finally, the commission emphasizes the need for special efforts to protect juvenile informants.


The use of criminal informants is an essential aspect of criminal investigations. It is also an area in which the potential for abuse is enormous. An understanding of the issues associated with informant use and a policy regulating the use of informants can reduce the possibility of informant misuse. The solution, however, lies not in the creation of rigid policies, but in the continual reevaluation of the goals of the police and the extent to which those goals are appropriate in a democratic society.

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