Credit: Reveal

For its investigation, Left for Dead, Reveal analyzed data on unknown decedents throughout the U.S. reported by coroners, medical examiners and other local authorities to the National Missing and Unidentified Persons System.

The NamUs site launched in 2007, but it includes much older cases – some opened in the early 1900s. The data includes details such as sex, age, tattoos and other identifying characteristics.

Our analysis is based on data from the NamUs website, which contains more than 10,000 unidentified cases. Those cases are predominantly male, with more than three times as many males as females. About 900 cases were young adults or children.

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This information is based on data collected on Aug. 1. However, our interactive database, The Lost & The Found, contains regularly updated data from NamUs on unidentified individuals along with data on missing persons.

A second database obtained by Reveal through a Freedom of Information Act request in June included the manner of death for the decedents, which is not available in the online data. Almost 2,000 decedents were victims of homicide, 368 were classified as suicides, and for about 4,000 cases, the manner of death was not determined.

Analyzing age

The typical age cutoff for a minor is 18. Because age estimations for deceased individuals are less precise, we used a wider definition.

Forensic scientists analyze teeth, bones and joints to identify decedents. Forensic anthropology and odontology often can offer only limited characteristics about individuals. Depending on the remains that have been found, the age of a decedent can be as specific as a range of a few years or an estimate that spans decades.

The NamUs data contains three indicators for age: a minimum, a maximum and a categorical description, such as adolescent. We relied on the minimum and maximum age because those numbers come from autopsy reports and forensic studies. We employed the methodology used by the National Center for Missing & Exploited Children to determine whether cases are children or young persons: a minimum age of 17 or younger and a maximum age of 25 or younger, respectively.

In addition, we used the categorical description, called “estimated age,” to provide more context. In 77 cases, the minimum and maximum ages were both zero, but the category was inconsistent with that range. In one record, for example, a case with both minimum and maximum of age zero was labeled adult. We did not include those records in our count of young people.

Emmanuel Martinez

Emmanuel Martinez is a data reporter for Reveal. A graduate of UC Irvine, Martinez received his master’s degree from the University of Southern California, where he studied radio and data journalism. Prior to joining Reveal, he interned for KPCC, the Los Angeles NPR affiliate, where he helped reporters acquire, clean and analyze data. Martinez is based in Reveal’s Emeryville, California, office.