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INDIANAPOLIS, Ind.- On Thursday, investigators say they had recovered DNA evidence from the Delphi crime scene where two girls, 13-year-old Abby Williams and 14-year-old Libby German, were found murdered.

That evidence now has top priority for processing by investigators. It’s a strong lead, in a case where authorities have been clamoring for any clue about the murderer. But just how important could is this DNA evidence be?

It is now the third piece of evidence investigators have said publicly they have: the grainy suspect photo, that chilling audio of a man’s voice saying “down the hill,” and now some kind of DNA sample.

“We asked for a fast-track as far as that piece information,” said Carroll County Sheriff Tobe Leazenby. "So I can’t go into specifics because of the ongoing [investigation].”

Police haven’t said specifically what kind of evidence they recovered, but DNA forensics expert Dr. Gay Bush says that evidence could be anything.

“It can be items found at the crime scene such as a cigarette butt, or a bottle, or a cup or a straw,” said Dr. Bush. “Or it can be bodily fluids if there’s some kind of assault.”

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Dr. Bush is the laboratory director for Strand Diagnostics, an FBI-accredited facility that often assists law enforcement, although they’re not working on the Delphi case.

“You can generally get a good profile if you’ve got at least 30-35 human cells,” said Bush.

It can sometimes take two days to a week to generate a DNA profile from evidence, if not longer.

“But if you are fast-tracking it…if it’s a case that’s got some urgency to it, it can be done in a couple of days,” said Bush.

Which is what Sheriff Leazenby said is happening. But while DNA can bolster a case, Dr. Bush says it’s not always a slam dunk on its own.

“It’s good,” said Bush, “the science is excellent, it’s very trustworthy, and there are very strong standards in DNA processing, but…when all is said and done, [it’s] just one piece of evidence for the process.”

Once a DNA profile is generated, it’s compared to a national database of DNA profiles. A best-case scenario would be if the profile from the crime scene matches with a suspect who’s profile is already on record. It could also match with an unknown profile, which is DNA that has been collected and documented, but never connected to a specific person.