It's a problem for police, and for the families of missing persons: bodies found that cannot be identified.
The city's Medical Examiner is trying to do something about it with an event this weekend. NY1 Criminal Justice Reporter Dean Meminger spoke exclusively to one family that tragically had to use the DNA program to find out what happened to a missing loved one.
It's been a heartbreaking month for Luis Marchan and his family; they finally buried his brother, Manuel, after he had been missing nearly four years.
"It is sad, but we needed to know what's going on with him," Luis Marchan said from Ossining. New York. "So now we know he's not with us anymore."
The family says they paid $8,000 to smugglers, known as coyotes, in 2013 to bring Manuel from Ecuador to Mexico and illegally across the border into Texas.
"You know, the economy in my country is not so good," Luis said. "He has family, and we are here and he tried to come here."
But Manuel disappeared during his journey. His worried family eventually contacted the New York City Medical Examiner's office, which helps to find missing people.
It's a program it will highlight Saturday at its third annual Missing Persons Day.
"There are tens of thousands of unidentified people in graveyards throughout the United States, and there are upwards of a 100,000 missing person cases right now," said Mark Desire, the assistant director of the Medical Examiner's office.
"We have a thousand cases just in New York City. We don't know who they are," Desire said. "We don't have any samples to compare to for the families."
The program collects DNA from relatives of missing people, and submits it to a national database.
"A sterile medical swab, we collect just a tiny bit of saliva — that's all we need," Desire explained.
The DNA from the Marchans matched the DNA from a body found in Texas.
The family learned that Manuel's body was found in the desert, and had been there for a while. They still don't know how he died.
"We hoped one day he'd call, but now we have to understand that is not going to happen," Luis said.
They're glad they provided DNA so they could have closure.
For more on Missing Persons Day, call 212-323-1201, or go to nyc.gov/missingpersonsday
DNA will be collected Saturday at the Medical Examiner's office on First Avenue and 26th St.