| On the morning of January 29, 1992, the body of 31-year-old Cheryl Walker was found by a small creek that ran through the Eastmont neighborhood of Oakland, California.
Walker was naked, her body bruised and mutilated, with a rope wrapped around her neck. Officers with the Oakland Police Department did not find any clothing near Walker’s body, and there were no signs her body had been dragged.
Two people who lived nearby said they heard screaming from the creek area. One said the screaming occurred around 10:30 p.m. on January 28; the other said it occurred around 4 or 5 a.m. on January 29.
Two weeks later, at 3 a.m. on February 11, the body of 23-year-old Marsha Gulley was found a few blocks away. She had been stabbed 33 times, and her pants had been pulled down.
In both instances, police collected several pieces of evidence from the bodies, including oral and vaginal swabs.
During the investigation into Gulley's murder, police learned that Deborah Norman last saw Gulley around 2:00 a.m. on February 11, an hour before her body was found. Norman said she and Gulley were riding around in a car driven by Marke Taylor, and that Taylor had just dropped Norman off at home before he and Gulley drove off. Police interviewed Taylor. He acknowledged giving Gulley a ride but said he wasn’t involved in her death. Police searched his car and found a bloody glove in the vehicle. Testing excluded Gulley from that evidence.
The investigation ran cold for eight years. In 2000, the police requested additional testing on biological material from the Walker and Gulley swabs. A criminalist would later testify that she did not initially proceed with DNA testing of the Gulley sample because she did not observe any sperm on the collected evidence. In 2001, she tried again. This time, she observed two sperm, but she said no testing was performed because the sample did not contain enough DNA to pass the sensitivity threshold of the kits used by the lab.
With regards to the Walker sample, testing was completed in 2001 but not submitted to the FBI’s Combined DNA Index System, known as CODIS, for two more years. In 2003, the FBI said 39-year-old Patrick Willis’s genetic profile was consistent with a partial profile found on Walker’s oral swab. In 2006, the police asked for testing of genetic material found under Walker’s fingernails. That testing didn’t occur until 2009, and those results also said the material was consistent with Willis’s genetic profile.
Willis was arrested in 2010 and charged with murder in Walker’s death. The charge was dismissed after the Alameda County District Attorney said there was insufficient evidence.
Separately, in 2011, the police requested another analysis of the Gulley swabs. This time, four sperm were observed on one of the swabs, and lab technicians were able to use equipment not available in 2000 or 2001 to recover sufficient DNA for testing. That testing included Willis as a potential contributor to the partial profile on Gulley’s swab.
Police arrested Willis on December 6, 2012, and charged him with two counts of murder. Along with the forensic evidence, the state had circumstantial evidence; Willis’s mother lived near where both victims were found.
Willis’s trial in Alameda County Superior Court began in July 2013. The murders were now more than 20 years old, and Willis faced a challenge locating witnesses. Norman died in 2008. Willis’s attorney filed a motion for updated address information for Taylor. The state refused to provide it, and the trial judge denied the defense attorney’s motion to compel it from the state. Separately, prosecutors argued the statements Norman and Taylor made to the police couldn’t be used at trial, because they were considered hearsay. The judge agreed.
Willis admitted that he had sexual contact with both women, who were sex workers, which would explain the DNA evidence. He denied, however, that he killed either one.
Along with the DNA results, the state presented expert testimony regarding “sperm persistence theory” in an effort to establish a time frame between Willis’s contact with the women and their deaths.
All biological material has a rate of degradation, which can depend on such variables as temperature or exposure to chemicals. In the vaginal cavity of a living person, the state’s expert said, sperm can live up to two weeks. In a person’s mouth, the degradation happens much more quickly because of saliva. But death stops the production of saliva, slowing the degradation.
Referring to sperm persistence in a person’s mouth, the expert said, “If I found a few sperm with no tails, I would say more than likely that it was deposited after about six hours or so, if even I can say that much. I would not expect to see sperm in an oral cavity much past 6 to 8 hours, maybe 12 hours maximum.”
In closing arguments, the prosecutor said that the expert’s sperm-persistence calculation showed that Willis killed Walker. She said the science indicated that the sperm found in her mouth could not have been deposited much before 11 p.m., roughly six hours before her body was found and around the time that a neighbor heard screaming.
Regarding Gulley, the prosecutor said, “There was ... sufficient sperm found for DNA testing which again tells you that the time that the sperm was deposited happened close in time to when Marsha was killed.”
Willis’s attorney said in his closing arguments: “The coincidence of sperm being found in the mouth of the two victims does not cause one to believe or accept a theory that somehow or another that means that he committed a murder of these two victims.” He said the DNA evidence established only that the defendant had sexual contact with the victims, and even under the sperm-persistence theory the “very small amount of sperm” found on the oral swabs establishes that the actual sexual conduct could have taken place up to 24 hours before death.
The jury convicted Willis of two counts of first-degree murder on July 22, 2013, and he was later sentenced to life in prison without parole.
He appealed his conviction, first arguing that the time lag between the crimes and the charges prevented the presentation of exculpatory evidence. While that appeal was pending, Willis, now represented by Shannon Chase through the First District Appellate Project, filed a state petition for a writ of habeas corpus claiming that his attorney had been ineffective for failing to challenge the trial court’s ruling that barred the use of the Taylor and Norman statements. When the court excluded those statements, the petition argued, his attorney should have moved to dismiss the charges.
The state argued that the statements “would not have provided the foundation to permit the defense to argue that Taylor killed Gulley because ... while Norman may have placed Gulley and Taylor together less than an hour before Gulley's death, there was no direct or circumstantial evidence connecting Taylor to Gulley's killing.”
After a judge in Alameda County Superior Court denied Willis’s petition, California’s First District Court of Appeal reversed and granted him a new trial on April 29, 2019.
The court said that balancing the prejudice from the absence of Norman’s statement against the state’s reasons for the delay in charging Willis, “we conclude that defendant's right to a fair trial required either that the charges against him be dismissed or that the defense be permitted to introduce the police report containing the hearsay evidence of what Norman observed at 2:00 a.m. the night of the Gulley killing. Trial counsel thus provided ineffective assistance in failing to file a motion challenging the pre-charging delay.”
The appellate court said that there was no evidence suggesting that the police had failed to use reasonable diligence in testing genetic material in a timely manner. Instead, the delays were due to changing technology and a cold case that had fallen off the radar.
Despite the DNA evidence linking Willis to both women, Norman’s statement gave context to the events the night Gulley was killed. “The fact that Gulley was seen alive within an hour of her death makes it less likely that defendant was the killer,” the court wrote, adding “Without the premise that defendant murdered Gulley, it is reasonably probable that defendant would not have been convicted of killing Walker.”
Willis’s retrial in Alameda County Superior Court began in May 2021. He was now represented by Ernest Castillo. Willis again testified in his own defense and said he had traded drugs for sex with Walker and Gulley but didn’t kill them. In addition, Castillo was able to introduce Norman’s statement about Gulley’s activities on the night she died.
Separately, Castillo located Taylor, who testified that he didn’t kill the women. But Castillo was able to raise doubt about his truthfulness after presenting testimony that twine found in the trunk of his car was similar to twine found near Gulley’s body. There was also new forensic evidence; material found in a pubic-hair combing of Gulley excluded Willis as a contributor.
Castillo also argued that the state’s forensic evidence pointing to Willis was misleading; Willis was accused, he said, simply because his samples were the only ones properly collected and preserved.
On May 5, 2021, the jury told the judge they were hung, and a mistrial was declared. Jurors told Castillo they were leaning 11-1 in favor of an acquittal.
“Just because [Willis] had sexual interaction with both of these women, that doesn't make him a killer, and I think the jury bought into that,” Castillo said.
While Willis had remained incarcerated after his conviction was vacated, he was released on May 11, 2021. Two weeks later, on May 24, 2021, prosecutors dismissed the charges. In 2023, the state of California awarded Willis $441,842 in compensation.
– Ken Otterbourg
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