DNA analysis helps heat up Lancaster County cold case

LANCASTER COUNTY, P.A. --- In December 1992, Christy Mirack was murdered in her East Lampeter Township home.

In october, after nearly 25 years of investigating, Lancaster County District Attorney Craig Stedman said the last viable suspect was cleared by investigators, leaving them with "literally" nothing to go on.

"Where that left us was just a case file sitting on a desk, hoping someone would call and somethings going to break. So, basically, just luck," said Stedman.

The district attorney`s office, looking for new hope, sent crime scene DNA to Parabon Nanolabs.

It led to composite sketches, created by DNA analysis, of Christy Mirack's killer at age 25, 45, and 55 - or at least an approximation.

"They offered sciences providing a new avenue that we didn't have before," said Stedman.

That science found can be found in a quiet office in Reston, Virginia - just west of Washington, D.C.

It's not your stereotypical lab with microscopes and petri dishes but with computers.

Dr. Ellen Greytak, Director of Bioinformatics, said Parabon Nanolab's inception came from the department of defense's anti-terrorism efforts.

"If there was an unexploded IED in a war zone, they'd swab DNA from it. Is there any information they can learn about that person? Mostly their physical traits but also who they might be related to if they had other samples to compare it to," said Dr. Greytak.

Parabon Nanolabs is now assisting law enforcement in the U.S.

A swab of blood or a rape kit is sent to their partnering labs in the Atlanta, Georgia area and Oklahoma.

"They're basically taking the sample, which has cells that contain DNA and they're extracting the DNA, then analyzing it to turn it into data," said Dr. Greytak.

She said that data is a sequence of letters.

Dr Gretyak explained that everything about us, including hair color, skin color, eye color, comes in a series of A, C, G, T.

"In one person, it goes AGGT and another person might go AGAT and the fact that that sequence is different might be why the first person has brown eyes and the second person has blue eyes," said Greytak.

From those letters, a composite prediction is created with computer software.

Predictions of eye, hair and skin color, as well as freckling of the face and ancestry of an individual are compiled just from that sample of DNA.

The image predicts the person at age 25.

Then, a forensic artist enhances the image to predict for older ages, such as 45 and 55.

The key word: predict.

Greytak said their composite sketches are created based on confidence and exclusion...it`s not exact.

"There's a lot of information about appearances not written in DNA...So we can only predict things that are written in the DNA," said Greytak.

Predictions also can not take into account how you live your life, for example diet or drugs.

But they say their composites serve as a "genetic witness," in cases where there are none.

A key part of their work is eliminating suspects, not specifically identifying them.

"What we're telling them is, okay, that person has brown eyes and we said 99 percent probability the person doesn't have brown eyes so that person might not be where to start your investigation...At the end, it's always going to be that standard DNA match that confirms the identity of that person. This is only going to help lead to that person, not identify them," said Greytak.

Stedman said ​the process of elimination is huge help for investigators.

"Maybe in that case we can eliminate Caucasians or in that case we can eliminate African-Americans based on the genetics. That saves a lot of resources for investigators," said Stedman.

For the Christy Mirack cold case, Stedman said they're sifting through more than 100 tips submitted since the release of the composites a few months ago.

They`re considering avenues and suspects that weren't considered before, putting the case back on a front burner.

"We have work to do. We're doing work on this case now that if we hadn't done this, we wouldn't have done anything," said Stedman.

The science of DNA isn't new but Stedman said its "changing the landscape of law enforcement" at an exponential rate.

"We need much less material than we needed before. We're able to have greater statistics to really identify the person. This is only going to get better," said Stedman.

Dr. Greytak said Parabon Nanolabs has worked on 150 cases around the country.

20 percent of the cases were solved after they got involved.

Greytak said their next goal is refining age prediction based on DNA samples.

They also believe predicting features such as curly hair and balding could come in the future.

If you or someone you know wants to share any information regarding the Christy Mirack cold case, visit a tips forum website here.