Defendant's DNA not in second sample from victim
Another DNA expert examines a 2012 report and says it allows for the possibility of another man at crime.
This story refers to violent acts and may be disturbing for some listeners.
The defense in the Sophie Sergie murder trial says a man other than defendant Steven Downs, left his DNA on the victim.
Sergie was found murdered in the bathroom on a woman’s floor of a Fairbanks college dormitory in 1993. Previous experts had testified the sample results were “inconclusive” and not up to scientific standards for comparing.
Many samples of fluids were taken by investigators at the crime scene and autopsy in 1993. But two have been prominent in this trial. Swabs of a liquid in the victim’s genitals, were tested for DNA that was eventually amplified and made into a profile the prosecutors say matches Steven Downs. He gave a DNA sample to the city police in Auburn Maine and the Alaska State Troopers before being arrested in 2019.
The second sample being discussed came from the victim’s breast.
“His DNA was not present on that breast swab,” said Dr. William Joseph Watson, a forensic DNA specialist who now supervises New Mexico’s criminal DNA analysis.
When she was found, Sergie’s shirt and bra were pushed up above her right breast. In 1993 and again in 1999, the Alaska Scientific Crime Detection Laboratory was not able to develop a useable DNA profile from the swabs used to collect the liquids.
Years later, in 2012 the case was opened again. DNA amplifying and analysis techniques had greatly improved. Alaska investigators sent what remained of the swab to Sorenson Forensics, a private DNA testing firm in Utah for analysis. That lab’s 2012 report also said their tests for DNA were inconclusive because the DNA profile was too weak to meet the thresholds for comparing to someone else’s DNA profile.
But, Watson said, it did find enough Y chromosome in the sample to show part of it came from a male.
“We can look at the balance between the X and the Y. And we can make some determinations about whether or not there is a male present. And in this case, it's a mixture of at least two individuals with at least one of them being a male.”
Watson was asked by the defense to re-examine the 2012 report. He said the other contributor to the sample, a female, was likely Sophie Sergie herself.
DNA sequencing reports are usually developed into an electropherogram that’s a graph that shows the length of specific DNA fragments displays, usually as peaks. At each specific position on a specific chromosome is an allele. We get two alleles for each gene, one from each parent.
Watson went a step further than other investigators, and said the profile in the Sorenson report DID have enough data to exclude Steven Downs, meaning that another man touched or talked over the victim’s body.
He said the numbered alleles at those specific spots on the unknown DNA did not match up to Downs’ alleles.
“And when we look at Mr. Downs, he has a 12 and 14. So we would say at this location, he is not included as a contributor. The reason why is because we don't see a 12, there is no 12 in the profile that was generated from the breast swab,” he said.
Earlier in the trial, Troopers, EMTs and examiners at the crime scene testified they could not remember if they wore masks or gloves in 1993. Same with people moving the body to the to the crime lab and during the autopsy – nearly all of them were male.
Closing arguments in the case are scheduled for Monday morning, and the case is expected to go to the jury Monday afternoon.
KUAC received prior permission from Fairbanks Superior Court to use recordings of the trial for this story.