On February 10, 2000, in Chicago, Illinois, a young woman named L. J. was abducted while walking home from work. The perpetrator forced her into his car, raped her, robbed her of money and other personal items, and pushed her out into the street.
L. J. ran home and reported the attack to her mother, who called the police. An ambulance took L. J. to the hospital, where doctors treated her wounds and took a blood sample and vaginal swabs for a sexual-assault kit. A Chicago Police detective collected the kit, labeled it with an inventory number, and sent it under seal to the Illinois State Police (ISP) lab.
At the ISP lab, a forensic scientist received the sealed kit. He conducted a chemical test that confirmed the presence of semen on the vaginal swabs, and he then resealed the kit and placed it in a secure evidence freezer. During the period in question, the ISP lab often sent biological samples to Cellmark Diagnostics Laboratory in Germantown, Maryland, for DNA testing. There was evidence that the ISP lab sent L. J.’s vaginal swabs to Cellmark for testing and that Cellmark sent back a report containing a male DNA profile produced from semen taken from those swabs. At this time, petitioner was not under suspicion for L. J.’s rape.
Sandra Lambatos, a forensic specialist at the ISP lab, conducted a computer search to see if the Cellmark profile matched any of the entries in the state DNA database. The computer showed a match to a profile produced by the lab from a sample of petitioner’s blood that had been taken after he was arrested on unrelated charges on August 3, 2000. On April 17, 2001, the police conducted a lineup at which L. J. identified petitioner as her assailant. Petitioner was then indicted for aggravated criminal sexual assault, aggravated kidnaping, and aggravated robbery.
Petitioner’s bench trial began in April 2006. In open court, L. J. again identified petitioner as her attacker. The State also offered three expert forensic witnesses to link petitioner to the crime through his DNA. First, Brian Hapack, an ISP forensic scientist, testified that he had confirmed the presence of semen on the vaginal swabs taken from L. J. by performing an acid phosphatase test. Second, Karen Abbinanti, a state forensic analyst, testified that she had used Polymerase Chain Reaction (PCR) and Short Tandem Repeat (STR) techniques to develop a DNA profile from a blood sample that had been drawn from petitioner after he was arrested in August 2000. Third, the State offered Sandra Lambatos as an expert witness in forensic biology and forensic DNA analysis.
Lambatos testified that, based on her own comparison of the two DNA profiles, she concluded that petitioner cannot be excluded as a possible source of the semen identified in the vaginal swabs, and that the probability of the profile’s appearing in the general population was 1 in 8.7 quadrillion black, 1 in 390 quadrillion white, or 1 in 109 quadrillion Hispanic unrelated individuals. The Cellmark report itself was neither admitted into evidence nor shown to the factfinder. Lambatos did not quote or read from the report; nor did she identify it as the source of any of the opinions she expressed. The trial court found petitioner guilty of the charges against him. The state court of appeals affirmed in relevant part, concluding that Lambatos’ testimony did not violate petitioner’s confrontation rights because the Cellmark report was not offered into evidence to prove the truth of the matter it asserted. The Supreme Court of Illinois also affirmed. The Supreme Court granted certiorari.
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