The crime-scene fingerprints did not match Baker's, and he was never charged with Sylvester's killing. He died in 1978.
The investigation into Sylvester's death went cold.
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When a match is far from a lock
The odds of an error are greater than you might think in 'cold hit' cases, which tap databases to ID suspects.
DNA: GENES AS EVIDENCE
For The Record
Los Angeles Times Thursday, May 29, 2008 Home Edition Main News Part A Page 2 National Desk 2 inches; 82 words Type of Material: Correction
DNA evidence: A May 4 article in Section A about the statistical calculations involved in describing DNA evidence in a murder case contained an arithmetic error. It said that multiplying the probability of 1 in 1.1 million by 338,000 was the same as dividing 1.1 million by 338,000. Actually, it's the same as dividing 338,000 by 1.1 million. The answer, a 1 in 3 probability of a coincidental match between crime scene DNA and genetic profiles in a state database, was correct.
For The Record
Los Angeles Times Sunday, June 01, 2008 Home Edition Main News Part A Page 2 National Desk 2 inches; 80 words Type of Material: Correction
DNA evidence: A May 4 article in Section A about the statistical calculations involved in describing DNA evidence in a murder case contained an arithmetic error. It said that multiplying the probability of 1 in 1.1 million by 338,000 was the same as dividing 1.1 million by 338,000. Actually, it's the same as dividing 338,000 by 1.1 million. The answer, a 1-in-3 probability of a coincidental match between crime scene DNA and genetic profiles in a state database, was correct.
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Getting a cold hit
In 2004, San Francisco police received state funding to test DNA evidence from unsolved homicides.
A crime-lab analyst retrieved from storage a swab that had been taken from Sylvester's mouth back in 1972. It contained sperm presumably left behind by her assailant. Though the sample was severely degraded, the analyst was able to develop a partial DNA profile.
Most profiles examine 13 genetic markers, usually enough to distinguish between two people. The sperm sample produced only 5 1/2 and was mixed with traces of DNA from another person, probably Sylvester, the analyst determined.
It was too little information to search California's DNA database; for that, at least seven markers were needed. To bridge the gap, the analyst used evidence from additional markers that were too faint to be considered conclusive. When this profile, now expanded to the necessary seven, was compared with the 338,000 profiles of convicted offenders in the state's database, investigators got a cold hit.
The profile matched Puckett's.
His genetic information was in the database because he had pleaded guilty to two rapes and a sexual assault in the Bay Area in 1977, five years after Sylvester's killing. After his release in 1985, he had committed misdemeanor battery, but since 1988 his record had been clean.
On Oct. 12, 2005, San Francisco Police Inspector Joseph Toomey knocked on the door of the Stockton mobile home where Puckett lived with his wife.
Puckett hobbled to the door clutching a bag of urine, explaining that he had just had triple-bypass heart surgery, Toomey later testified. During a 2 1/2 -hour interview, Toomey showed Puckett photos of Sylvester and the crime scene.
"You never had sex with that girl?" Toomey asked.
"No," Puckett said.
"You've never been in the house we showed you?"
"No."
Puckett volunteered to give Toomey a fresh sample of his DNA.
When it matched the same markers as the earlier test, Puckett was arrested and charged with murder.
Crucial evidence
The case was assigned to the San Francisco public defender's office, which had recently hired a DNA specialist named Bicka Barlow.
