In Virginia thousands of felons failed to submit their DNA to the state's database as required by law, partly because state and local agencies failed to require the samples, The Washington Post reports.
The discovery has led to a massive review of the DNA database but the current estimates are that the state is missing samples from 20 percent of the state's felons. State law requires that all convicted felons and those arrested in connection with violent crimes contribute a genetic sample to the database.
"The good news is it appears that we have well over 80 percent of convicted felons in the database, but obviously we need to have 100 percent of them in the database," said Clyde Cristman, deputy secretary of the Virginia Department of Public Safety.
The database has been a huge win for law enforcement, scoring some 3,600 "cold hits," in which police investigators match genetic material obtained from a crime scene to offenders in the database.
Scores of violent crimes, including some homicides, have been solved that way. Virginia's database, like that of other states, forms part of a larger national DNA network that has similarly produced millions of cold hits.
Gaps in the state database could diminish the effectiveness of DNA as a crime-fighting tool, officials said. "In order to maximize effectiveness of the national DNA database, it is important to collect DNA samples from all persons authorized by state and federal legislation," said Ann Todd, a spokeswoman for the FBI crime lab.
The gaps came to light when Charlottesville police investigating a series of rapes discovered that 125 felons - 20 percent of the 600 supervised felons in the area - were missing from the system.
But Virginia crime lab director Paul Ferrara said this week that he became aware of a possible problem earlier when a review last year of the state's more than 13,000 registered sex offenders uncovered 3,149 missing DNA profiles, or about 24 percent of the state registry.
"I'm not surprised that there are missing felons," Ferrara said. "What would be surprising is the magnitude. That's the thing we're not sure on."