Confidential informants (CIs) are an important component of law enforcement investigations. However, they also come with intrinsic problems (e.g., association with criminal offenders, drug and alcohol dependency, a criminal history of their own, which may include fraud, deceit, or violence), and they are incentivized to lie and fabricate details of their work when facing a (potentially lengthy) custodial sentence, which may jeopardize the integrity of criminal cases. To mitigate these and other control issues, the police should test a prospective CI’s integrity before they are deployed to work on a given case. In addition, the agency should promulgate a comprehensive written policy on CIs that adopts the best-practice principles identified by the International Association of Chiefs of Police (IACP). Problems that arise when using CIs may be linked to the failure of the police to test their integrity prior to allowing them to work, as well as issues related to training, supervision, and control.