OCR Text |
Show HERALD DAILY A14 May 8, 2008 Thursday, DNA evidence: The odds of justice can be long Jason Felch and Maura Dolan LOS netic markers, usually enough to distinguish between two TIMES ANGELES Christmas tree. a scream. For more than three decades, Sylvester's slaying went unsolved. Then, in 2004, a search of California's DNA database of criminal offenders yielded an apparent breakthrough: Badly deteriorated DNA from the assailant's sperm was linked to John Puckett, an obese, wheelchair-boun- d with a s s . , ... his- tory of rape. ROBERT DURELLLos Angeles Times , The DNA "match" was based on fewer than half of the typically used to connect someone to a crime, and there was no other physical evidence. Puckett insisted he was innocent, saying that although DNA at the crime scene happened to match his, it belonged to someone else. At Puckett 's trial earlier this year, the prosecutor told the jury that the chance of such a coincidence was 1 in 1.1 million. Jurors were not told, however, the statistic that leading scientists consider the most significant: the probability that the database search had hit upon an innocent person. In Puckett's case, it was 1 in 3. The case is emblematic of a national problem, the Los Angeles Times has found. Prosecutors and crime labs across the country routinely use numbers that exaggerate, the significance of DNA matclv es in "cold hit" cases, in which a suspect is identified through a database search. Jurors are often told that the odds of a coincidental match are hundreds of thousands of times more remote than theyy actually are, according to a review of scientific literature and interviews with leading at his trial John Puckett right confers with his attorney, Kwixuan H. Maloof, in San Francisco. "We're making love!" The FBI lab, which oversees Nigodoff returned to her the nation's offender databases, apartment and called police, has disregarded the recomwho found Sylvester's body. mendation of its own adviThere were no signs of forced sory board, bureau officials ac- deteriorated. entry or a struggle. Prosecutors say they don't knowledged. So far, the courts Initially, police focused on have ruled in law enforcement's mention the database problem a street artist named Robert favor on this issue. to juries because it could unfair- Baker, then 32, who had reAs a result, some experts ly reveal that a defendant has a cently escaped from a mental institution. He had been identifear, a technology best known criminal record. They also say fied as a suspect in a rape that for freeing the innocent could that using more conservative statistics would not make a difbe causing its own miscaroccurred two weeks before ference in many cases, because Sylvester's killing and four riages of justice. For years, police used DNA the odds would still overwhelm- blocks from her apartment. The victim in that earlier case only to compare a crime-scen- e ingly favor the prosecution. Now the California Supreme and a friend identified Baker as sample to a single person they Court is weighing the statistihad other reasons to suspect. the rapist, but for reasons that cal and other concerns raised In court, prosecutors could leare now unclear, authorities degitimately cite the remote odds by cold hit cases t- - the highest cided they did not have enough court yet to consider them evidence to prosecute him that someone selected at random off the street would share People vs. Nelson, which inBaker also was identified as volves the 1976 murder of a the same genetic profile. the man who, four days after But in cold hit cases, the incollege student in Sacramento, Sylvester was killed, harassed a woman and a young girl and vestigation starts with a DNA is scheduled for oral argufollowed them to their home match found by searching ments Thursday. It could influence how such a few doors from Sylvester's thousands, or even millions, of genetic profiles in an offender cases are tried across the apartment, police records show. database. Each individual com- country and undermine some He was not charged in that incident but he was booked parison increases the chance of convictions in California. a match to an innocent person. for the rape four blocks from It was three days before Nevertheless, police labs and Sylvester's apartment. Police thought he might also prosecutors almost always cal- Christmas, 1972, in an apartculate the odds as if the suspect ment building near San be Sylvester's killer. had been selected randomly Francisco's Golden Gate Park. In Baker's van, police found from the general population in. Helen Nigodoff, the building's a parking ticket with drops of a single try. authorities in the field. landlady, heard thumping and blood on it. The blood type was The problem will only grow other noises from the apartTwo national scientific comO, the most common, the same as the nation's criminal DNA ment above hers. as Sylvester's. DNA testing mittees, including the FBI's DNA advisory board, have databases expand. They alwas not available then. Nigodoff went upstairs to recommended portraying the The crime-scen- e fingerprints' ready contain 6 million profiles. check on Sylvester. The door The danger of implicating an to the apartment was open. She did not match Baker's, and he odds more conservatively. But innocent person through a cold saw a bearded man attempting interviews with expert witwas never charged with Sylvenesses and DNA analysts from hit becomes particularly acute to cover his face with his hand, i ster's killing. He died in 1978. "Go away!" he screamed, Ni-with crimes that are decades crime labs across the country , Theinvestigation into Syl-- , show that few if any have ad- - old, like Sylvester's killing. yester's death went cold. godoff later told investigators, 7 In 2004, San Francisco police received state funding to test DNA evidence from unsolved general-populatio- n general-populatio- n be told about the recommendation of two leading panels of scientific experts, one convened in the state's database, investiby the National Research Coungators got a cold hit. The procil and the other by the FBI. file matched Puckett's. Both committees settled His genetic information was in the database because he had upon a statistical remedy to pleaded guilty to two rapes and adjust for the many individual a sexual assault in the Bay Area comparisons made during a in 1977, five years after Sylvesdatabase search. It has been ter's killing. After his release in widely but not universally embraced by 1985, he had committed misdemeanor battery, but since 1988 T v In every cold hit case, the his record had been" clean. panels advised, police and prosOn Oct. 12, 2005, San Franecutors should multiply the cisco Police Inspector Joseph Random Match Probability (1 in 1.1 million in Puckett's case) Toomey knocked on the door of the Stockton, Calif., mobile by the number of profiles in home where Puckett lived with the database (338,000). That's his wife. the same as dividing 1.1 million Puckett hobbled to the door by 338,000. For Puckett, the result was clutching a bag of urine, exdramatic: a chance that plaining that he had, just had s the search would link an innoheart surgery, cent person to the crime. Toomey later testified. During David Merin, a deputy San a2 interview, Toomey Francisco district attorney, showed Puckett photos of Sylvester and the crime scene. argued that the statistical ad"You never had sex with justment recommended by the scientific panels would be "conthat girl?" Toomey asked. "No," Puckett said. fusing and misleading." "You've never been in the Superior Court Judge Jerome Benson ruled in favor of Merin. house we showed you?" In doing so, he followed a Cali"No." Puckett volunteered to give fornia appellate court ruling on the same issue. The jury would Toomey a fresh sample of his never hear the DNA. When it matched the statistic. .7' At 2:30 p.m. on March 6, afsame markers as the earlier test, Puckett was arrested and ter 48 hours of deliberation, the jurors filed into the courtroom charged with murder. The case was assigned to the with a verdict: guilty of murder in the first degree. San Francisco public defender's office, which had recently Puckett, now 74, sat motionless in his wheelchair. He later hired a DNA specialist named Bicka Barlow. was sentenced to life in prison, Barlow had earned a maswith the possibility of parole after seven years. His attorter's degree in genetics from Cornell University before goneys said they would appeal. Interviewed outside court ing to law school A veteran of after the verdict, jurors said dozens of DNA cases, she Puckett's the weakest 7 they had struggled to weigh ?: the different statistics. In the .match she had ever seen. Typically, prosecutors rely i end, however, jurors said on FBI statistics to estimate the j they found the statistic rarity of a particular DNA pro-fil- e in the general population. 7 Merin had emphasized to have This calculation is known as been the most "credible" and the Random Match Probability. "conservative." It was what allowed them to reach a unani: The chance that two un-- mous verdict. related people will share trie "I don't think we'd be here same 13 markers can be as if it wasn't for the DNA," said remote as I in a quadrillion Joe Deluca, a a number with 15 zeros, v old marBecause the match in Puckett's tial arts instructor. case involved only 5 12 genetic Asked whether the jury locations, the chance it was co- might have reached a different incidental was higher but still verdict if it had been given the remote: 1 in 1.1 millioa number, Deluca didn't hesitate. "Of course it would But Barlow thought this figure vastly exaggerated the have changed things," he said. "It would have changed a lot of strength of the evidence. It did not take into account how things." triple-bypas- 12-ho- con-sider- . : . ,5 homicides. A crime-la- b 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 ge general-populatio- n ' mmm state m mm f The figures used by prosecutors portray the odds of matching crime-scen- e DNA to a single, randomly selected person. But because database searches involve hundreds of thousands or millions of comparisons, experts say using the statistic can be misleading. Barlow argued during pretrial hearings that the jury should scientistSu. Witnesses have died, evidence has been tost and memories have faded. All of this puts greater weight on the DNA evidence, which also may have opted that approach. Puckett had been identified: through a search of a large database. people. The sperm sample produced only 5 12 and was mixed with traces of DNA from another persoa 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 expanded profile was compared with the 338,000 profiles of convicted offenders Police found the naked body of Diana Sylvester near her San FranThe cisco nurse had been sexually assaulted and stabbed in the heart. She lay on her back, her neck laced w ith scratches and her mouth open as if frozen in " 5 Mistakes People Can Make When Selecting A Back Pain Doctor , " . , Ef (3 Ef The high cost of lew priced medfcal procedures GJ NctviesAtBSfirrKxfelsbefcxehaxI Nctkrxwngthevite fWbeirigaencptionslDsele(Jfn3ni Mr "T - iiihirr T harm r nliforl rwr In troatmart mTu4u rnt'nyi Wiina! Aid fontorQ nf Amorira uo nffor a PDPP cninal riommrtroccinn rnnonlfatinn I V. IV. ' WW. lit,. V. VI rHIIWI IVW uuiflWI l u WM ,IW I INI y IUU1, nrtn.rirnn im IOUI Lti LIU1I uiujf up IUI U UW . ntAriMlna if uni i Ai A n aaa ttl aJ A ai ' nmh .4aaaa mama. W amI.aa a4 u....iiinlniilrt!il a aaa aa A ...a '..a e ii juu aica wuiuiuaic, uui wcu uuuu ufliauiiuiiiiuc ai mv.ojiiiaiaiu.i,uiii anu we ve aisu a. uctcii uui . :. . i. . i.. . i ni a a uvu rncc a iu iuu tan iweive uy yuu gupy uiiuctsujiiu. luycuiei neiy ampiy uwiny. 'At. Wf.i tft rnrr rir ntA. v l ui j Dr. Eric (001 ) 75G -7QOO . -.ii iim niii mi Lee, D.C. 364 East State Road - American Fork SpinalAid tt www.spinaiaid.com v ,:r K.- - tli'. 7 :if,,t(! X in c; rn:! dt a lost cause, she has ycu. - i:; b -- t hl- nd ti-- br77a:t can fail prey to meth addiction. heS; that ony Professional ... " .; Is. S'st "i treatment can provide. the recovery process now. For confidential 1 voit . t cnc:.r.;;U;ncY.org j 7 1 a 1 ; j : i: ! 1 JqVma I luLl O J j ii LZl U I Edison Stanford Hearing Center f -- For a limited time INTUIS fnr at lnwac rx e f ir A I 777 N 500 W dm Cm Pr month 'A AOC for 60 months f Doctor's Park Suite 005 Provo 373-588- 7 ....learn more stj'VWAv.utnhihownndscft.ccm |