Stephanie Ramos

Sandy eventually says he'll answer questions if his lawyer can be present.

Okay, the detective said, seizing the opportunity.

Call him and ask.

The detectives have no choice but to let Sandy leave, but not before he made one last bid for connection.

And I honestly, I hope so.

It's not looking good right now.

Sandy walked out the door, taking any hope of a confession with him.

Now, all the attention was on the crime scene evidence.

Investigators wondered if that would prove that Sandy Preer killed his wife.

But what it proved wasn't what detectives expected at all.

As we've covered in previous episodes, there was blood visible throughout the prayer house.

In the days after the murder, investigators meticulously combed through the crime scene, collecting samples of that blood to test for DNA.

State's attorney John McCarthy says his county was uniquely equipped to handle it.

It was Cellmark, and it was on Goldenrod Lane, and it was in Gaithersburg in the middle of my county.

DNA was first used in criminal cases in the late 1980s, but many people got a crash course on how it actually worked in the mid-1990s.

Six years before Leslie Prier's murder, the lab director of Cellmark was called to the stand in the so-called trial of the century.

In OJ Simpson's trial, the Salmark Lab in Maryland was asked by the prosecution to verify the DNA results of the LAPD crime lab, which they did, pointing to a one in 530 billion chance of error.

And despite the fact that OJ was acquitted by the jury, the case still proved just how compelling DNA evidence could be.

In 2001, that same lab, Cellmark, analyzed the DNA samples found in the Prier home, and they discovered something important.

A lot of the blood found at the scene came from Leslie Prier, but not all of it.