The National Center for Missing & Exploited Children (NCMEC) is a private, nonprofit organization established in 1984 by the United States Congress. In September 2013, the United States House of Representatives, United States Senate, and the President of the United States reauthorized the allocation of $40 million in funding for the organization as part of Missing Children's Assistance Reauthorization Act of 2013. The current chair of the organization is Jon Grosso of Kohl's. NCMEC handles cases of missing minors from infancy to young adults through age 20.

Unidentified decedent, or unidentified person, is a corpse of a person whose identity cannot be established by police and medical examiners. In many cases, it is several years before the identities of some UIDs are found, while in some cases, they are never identified. A UID may remain unidentified due to lack of evidence as well as absence of personal identification such as a driver's license. Where the remains have deteriorated or been mutilated to the point that the body is not easily recognized, a UID's face may be reconstructed to show what they had looked like before death. UIDs are often referred to by the placeholder names "John Doe" or "Jane Doe". In a database maintained by the Ontario Provincial Police, 371 unidentified decedents were found between 1964 and 2015.