‘170 septillion times more likely’ Expert testifies about DNA in UNC student murder trial

NC Crime Lab Forensic Scientist Erin Ermish was back on the witness stand in day seven of testimony in the UNC student murder trial.

Much of Ermish’s testimony on Wednesday focused on her lab reports from 2012 and 2013 in the months after Faith Hedgepeth was found murdered. 

Her reports at the time say DNA from a then-unknown person found on Hedgepeth’s body “could not be excluded” from also being found under her fingernails, her clothing, a blue Riesling wine bottle, a white bag with writing on it, a white and green pen found in the doorway of the apartment, and a Bacardi rum bottle prosecutors say was the murder weapon. 

On Thursday, Ermish testified about receiving the defendant Miguel Salguero-Olivares’ DNA in 2021.

With that new DNA, Ermish testified that DNA from swabs of Hedgepeth’s body was a mixture of two individuals, saying Salguero-Olivares’ DNA is “included as a possible contributor to this profile.”

Ermish testified that as a forensic scientist, she would not say DNA belongs to a specific person 100%, because “every person on earth has not had their DNA tested.”

“So instead,” Ermish said, “Every time a DNA standard matches a profile, we perform statistics to give an idea of common or rare that DNA profile might be.”

Her testimony was illustrated using two hypotheses.

Ermish said the DNA from swabs from Hedgepeth’s body is 170 septillion times more likely to a mixture of DNA from Hedgepeth and Salguero-Olivares, rather than from Hedgepeth and an unknown, unrelated individual.

One septillion is the number one followed by 24 zeros. For comparison, one billion is a one followed by 9 zeros.

Ermish also testified about the Bacardi rum bottle.

She said the mixture of DNA from the top of the bottle is 48.6 tredecillion times more likely to be from Faith Hedgepeth and Miguel Salguero-Olivares than two unknown, unrelated individuals.

A tredecillion is a one followed by 42 zeros.

Ermish said swabs from underneath Hedgepeth’s left fingernails was a mixture of three male contributors.

However, because the profile is inconclusive, it could only be used for exclusionary purposes; for example, whose DNA is not there.

“So the defendant’s profile could neither be included nor excluded?” ADA Angela Garcia-LaMarca asked. “Correct,” Ermish replied.

Ermish also performed testing on Hedgepeth’s clothing from that night.

DNA from the inside waistband of her shorts was interpreted as a mixture of two contributors, including at least one male. Ermish said it is 1.46 nonillion times more likely to be a mixture of Hedgepeth’s DNA and a male unknown than two unknown people.

Hedgepeth’s roommate, Karena Rosario, was excluded from DNA analysis of other pieces of her clothing.

Another test on a piece of clothing found a partial DNA profile from a mixture of three contributors, including at least one male.

Ermish said the third component was insufficient to compare, but Hedgepeth and Salguero-Olivares were included as possible contributors, and Rosario was excluded.

That mixture is 32.4 billion times more likely to be from Hedgepeth, Salguero-Olivares, and one other unknown person, than three unknown people.

Ermish testified DNA on the blue Riesling wine bottle found at the scene had a “partial profile consistent with the defendant’s DNA.”

A white bag with writing on it was also found near Hedgepeth’s body and tested.

Ermish said there was a predominant profile on that bag when it was tested in 2012, and that profile matched the predominant profile of Miguel Salguero-Olivares.

“The probability of randomly selecting an unrelated individual with a DNA profile that matches the predominant profile is approximately 1 in 61.6 quadrillion in the Hispanic population,” Ermish said in court.