Get a look inside a murder case where virtually everything from the first moments of the investigation through the verdict are captured on camera. Correspondent Richard Schlesinger reports in "The Case Against Sandra Garner," an all-new "48 Hours" airing Saturday, March 7 at 10/9c on CBS.

When you watch the video we included here, you'll see things you've never seen before. What's more, "48 Hours" has never seen it before, either … and let's face it, we've seen a lot. Police body cameras were rolling as they responded to Jon Garner's murder in Maypearl, Texas, on the morning of January 2, 2018.

Thanks to the body cameras they were wearing, it's as though we are all alongside the cops right from the moment they start investigating. And the cameras don't stop until the end of the investigation.

The video is gripping. When first responders enter the house, they hear a hysterical Sandra Garner scream "Please help him!" as she directs them to her husband's body.

You can feel the tension right after police arrive. A deputy asks Maypearl Police Chief Boyd Norton, "Are you sure he's not here anymore?" as they search the crime scene with their guns drawn, looking for a masked intruder. In that moment, you're following police from room to room as they clear the Garner home before they are sure they are safe.

We also hear Sandra Garner's story for the first time after the house is cleared. The whole conversation is caught on camera. She tells the officer, "I woke up and I had heard gunshots … I started screaming, hoping somebody would hear me … And he said shut up. I said please don't kill me. And he says, what I came here to do is done."

Throughout her story, Sandra Garner stays calm, walking investigators through what she said happened. "I knew I had to stay kind of calm to be able to tell them everything that happened," she told "48 Hours."

It's an important moment because it's the same story Sandra sticks to throughout the investigation.

But that consistency along with her demeanor would end up being questioned by police.

"She acted distraught. I never saw a tear. She didn't cry. And I did not think it was very genuine," said Chief Norton.

This was the first time Chief Norton was in charge of a murder investigation. The crime technician wouldn't arrive for another 8 hours, so he says, "I pulled my phone out … and I started snapping pictures" His bodycam shows him snapping dozens of photos of the crime scene and Sandra Garner. This footage would become critical at trial.

Eight days later, those same cameras captured Sandra Garner being arrested for murdering her husband Jon.

We see police vehicles on the Garners' driveway waiting for Sandra as she pulls up in her car. She is quickly handcuffed and placed in the back seat of a police car.

The hours of bodycam footage would play a huge role in Sandra Garner's trial in September of 2019, leaving prosecutors and defense attorneys to worry whether it would help or hurt their case. The answer was not what the police expected.