A stored DNA sample can wait years for the test that reads it

How did a 1987 saliva sample lead to the Green River arrest?

The Green River case began in 1982, when women and girls were found dead in South King County.^1,3 Police took a saliva sample from Gary Ridgway in 1987 but lacked the evidence to arrest him.^1,2 After the state crime lab began using a new DNA method on the case evidence in 2001, he was arrested on November 30, 2001.^1,2,4

Marcia Chapman, 31, Cynthia Hinds, 17, and Opal Mills, 16, were found in or near the Green River on August 15, 1982.^1,4 Carol Christensen, 21, was found near Maple Valley on May 8, 1983.^1,2,4 Their four deaths were the first murders Gary Ridgway was charged with, in 2001.^1,3,14

Ridgway passed a polygraph in 1984.^1,2 On April 8, 1987, police searched his home and vehicles and took bodily samples, but had insufficient evidence to arrest him.^1,14 Under a court order he chewed a piece of gauze, and detectives preserved it while they waited for DNA technology to improve enough to test it.²

In March 2001, the state crime lab began using a new DNA method on the Green River evidence.^1,14 Ridgway was arrested on November 30, 2001, and his DNA was linked to three of the four women he was charged with killing.^1,2,4 On November 5, 2003, he pleaded guilty to 48 counts of aggravated first-degree murder.^1,3

What is CODIS, and when did it start?

CODIS, the Combined DNA Index System, is the FBI’s system for comparing DNA profiles among crime laboratories. It began as a pilot project in 1990. The DNA Identification Act of 1994 formalized the FBI’s authority to establish a National DNA Index System, which became operational in 1998.^5,6

CODIS lets federal, state and local forensic laboratories exchange and compare DNA records electronically, linking serial violent crimes to each other and to known offenders.⁵ It has three levels, local, state and national, and profiles flow upward from local and state laboratories to the national index.⁶

The FBI says the program began in 1990 as a pilot serving 14 state and local laboratories.⁵ As passed in 1994, the DNA Identification Act authorized an index of DNA identification records of people convicted of crimes and of analyses of DNA samples recovered from crime scenes and from unidentified human remains.^6,7 The FBI says the national index was implemented in October 1998.⁵ The FBI distributed the CODIS software free of charge to state and local laboratories doing DNA analysis.⁶

The Justice Department’s Inspector General reported in 2006 that two indexes form the crime-solving capabilities of CODIS.⁶ The forensic index holds profiles from crime-scene evidence whose source is not known with certainty, and the convicted offender index holds profiles of people convicted of qualifying crimes.⁶ The FBI says matches between the forensic and offender indexes give investigators the identity of suspected perpetrators.⁵

How did a DNA database lead to three Los Angeles convictions?

Carol Alford, 41, was killed in Los Angeles in 1987, and Audrey Nelson, 35, and Guadalupe Apodaca, 46, in 1989.^10,11 All three cases were still unsolved when DNA linked them to one man.^9,10

DNA evidence from the Nelson and Apodaca cases was linked to Samuel Little through the California Department of Justice’s CODIS offender databank, according to the Los Angeles Police Department.^10,13 Detectives then had him arrested in Kentucky in 2012 on a Los Angeles narcotics warrant, and he was returned to California.^12,13 DNA evidence later connected him to Carol Alford’s murder as well.^9,13

The FBI says the Los Angeles Police Department notified its Violent Criminal Apprehension Program, ViCAP, in 2013, and ViCAP opened a full background investigation.⁹ In 2014 a jury convicted Little of the three murders, and he was sentenced to three consecutive life terms without parole.^9,11 In October 2019 the FBI said he had confessed to 93 murders and that 50 cases had been matched to him, with many more pending final confirmation.^9,12

What does a database need before it can name anyone?

The Justice Department describes CODIS as a database that compares DNA profiles from forensic samples with those of known offenders. If a search results in a confirmed match, a lead is generated and the matching offender’s name is released. If it does not, no lead is generated.⁸

Both cases on this page needed two halves: evidence from the crimes and a DNA profile of the man.^2,13 Ridgway’s half came from a court-ordered sample in 1987.² Little’s was already in the California Department of Justice’s CODIS offender databank, according to the Los Angeles Police Department.^10,13

Federal law also sets what goes in.⁷ The DNA Identification Act requires that the national index hold only DNA information based on analyses performed under the FBI’s quality assurance standards.^6,7

Under the Justice Department’s 2019 interim policy, a covered agency may attempt forensic genetic genealogy only after the forensic profile has been uploaded to CODIS and CODIS searches have failed to produce a probative and confirmed DNA match.⁸ The agency must also have pursued reasonable investigative leads, and the prosecutor must agree that genealogy is a necessary and appropriate step.⁸