For the John Does walking among us, their lives are mysteries to society and to themselves. These seemingly invisible citizens can't answer the simple questions, "What's your name?" or "Where are you from?" They are blank slates.
They aren't eligible for health insurance, can't pay rent or get a driver's license. They can't get a job or apply for unemployment benefits.
Many of them suffer from mental illnesses that render them unable to remember who they are. Scans of their fingerprints lead to no matches, indicating that they do not have criminal records. Their faces do not appear in databases for missing people.
In February, a man was brought to a Fort Worth, Texas, hospital with a cranial bleed. He did not know his name or remember any details from his life. He was admitted under the name "Bobby Jones," but only answered to "Smiley." They have guesstimated his age to be about 76. He can speak, but rarely answers questions. He is paranoid and no longer able to walk.
"I just keep thinking he was somebody's little baby once and you think about how much you love your children and what happened to his parents? Where have they gone?" wondered Kathleen Evans, the inpatient case manager for Fort Worth's JPS Health Network where Smiley was a patient.
The caretakers know that Smiley has been on the streets and in shelters in the Fort Worth area for about 20 years. He has no police record, proven by the lack of a fingerprint match. The hospital has been paying $24,000 every three months for his care, but Evans sees no other choice.
"We couldn't put him out on the streets," she said firmly. "I can't lay him out on the sidewalk. He's a human being and you have to send him to a safe place and the street would not be safe for him."
Smiley is now in a nursing home. Evans and the hospital tried every known avenue to search for his identity.
The National Missing and Unidentified Persons System (NamUs), working under the U.S. Department of Justice, has several databases, but does not currently have one that includes the living unidentified. But after being presented with a number of cases of living unidentified, they are developing a new database that they hope to launch by the end of this year.
"The traditional system is in dealing with unidentified deceased, but we know there are unidentified living," NamUs spokesman Todd Matthews told ABCNews.com. "We have to include the missing. They're missing from somewhere."
Matthews does not have an exact count on the number of cases, but NamUs is aware of "dozens" of men and women living without identities. He believes there are many more cases out there that have not been reported because hospitals and authorities don't know what to do with them.
"I think people have seen this as a homeless person and they've just fallen ill, but that's not always the case," Matthews said. "I think we're really going to have people to focus on this and see how many are out there."
"It's a real problem," he said.
Benjaman Kyle can tell you how big and bewildering the problem is. Kyle is a working, productive member of society, whose lack of identity is a daily struggle. He made up the name Benjamin Kyle just so he would have a name.
In August 2004, he was found naked, unresponsive and covered with fire ant bites behind a Burger King Dumpster in Richmond Hill, Ga. When he awoke in a hospital, he was confused.
"I had no idea who I was. I couldn't remember," Kyle told ABCNews.com. "I had no idea how I got there."