“DNA, It’s like looking at a blueprint”- Forensic details into the Jury Trial of Steven Downs
FAIRBANKS, Alaska (KTVF) - Forensic evidence slides, smears, and DNA test results were the main topics of discussion during the Friday, January 28, 2022 proceedings in the jury trial of Steven Downs.
Downs is accused of the alleged murder and rape of Sophie Sergie in a University of Alaska Fairbanks dorm bathroom on April 26, 1993.
The primary focus was cross-examination of two women who worked at the Alaska Scientific Crime Detection Laboratory in Anchorage, Alaska in 1999 and 2000. Both of the women had analyzed forensic evidence and DNA that was taken from the body of Sophie Sergie.
Kristin Denning, a former forensic scientist, took the stand first. She had re-examined slides prepared by Hayde Hamilton 6 years after Hamilton previously prepared them in 1993.
The reason for the re-examination of slides, Denning says, was the new developments in technology and DNA testing that had become available, such as Short Tandem Repeat or STR Analysis for DNA profiling. Also, when Hamilton initially looked at the samples there were no suspects in Sergie’s death. She said, “We are now bringing online STR’s, and so we wanted to go back especially to the samples - and the easiest way is to do that is a quick peruse of the smears again, a re-examination of the smears and slides to decide which of the samples that were submitted would be more suitable to go forward.”
Denning stated that Hamilton’s initial examination was done within reason at the time and it is not unusual or uncommon for other scientists to re-review data collected. In fact, the practice is done often to establish accuracy within data collecting and reports.
After the re-examination, Denning was able to find more valuable semen specimens that were later used as possible DNA samples.
When it came to analyzing that DNA, the testimony came from Abirami Chidambaram.
She received blood and semen samples taken by both Hamilton and Denning in May of 2000, where she then began deciphering the DNA.
“Were these the sample profiles or were they different?” asked Alaska State Prosecutor Christopher Darnall.
“Oh, they were definitely different. To start with Sophie Sergie’s sample came out with a female and the foam fraction obviously had an XY which meant it was a male,” said Chidambaram.
On the profile Chidambaram generated on May 17, 2000, Darnall asked Chidambaram, what kind of statistical analysis she performed on her results.
She stated that she looked at various frequencies when looking to identify a possible ethnicity of the sample DNA.
“We just want to know which confidence we can place on a match because in this particular case it was an unknown sample anyways. But we would also like to know what exactly is the, [sic] let’s say we find a match, how much confidence is it? Is it one in four, one in three? Is it common like every third person on the street could match? Or is it so rare that only this one person could match it?” Chidambaram said.
Darnall followed the question of whether there was a good DNA profile and what the statistics were on identifying a person.
“We are talking one in trillions and quadrillions, which is much more than billions,” she replied.
He asked in this specific case what the DNA read. “The Caucasian gave me the frequency of one in forty-one quadrillion,” said Chidambaram.
“So what does that number mean if someone matches the profile generated?” asked Darnall.
“Unless that person has an identical twin, it is very unlikely someone else is going to match that profile,” she assured. Darnall replied, “What are the chances of someone else matching that profile be based on your statistical analysis?”
“Zero,” said Chidambaram, “as long as there is no identical twin.”
She stated just looking at the DNA molecules, “it’s like looking at a blueprint, it gives a snapshot of how to identify a person at the molecular level.”
In cases considered “Cold Cases”, DNA can go into a database called CODIS where it is stored until there is a potential match to be considered in solving the case.
Our Station was granted authorization to use Video recordings of this trial from the Alaska Court System.
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