Mike Boettcher

Okay, we got the whole fam family. Steve's an accident reconstructionist. He's used to speaking to juries in courtrooms. He's dressed the part today in a light gray suit coat and tie. Anyway, I just feel better knowing who I'm talking to.

Why did Karen's car leave the road that night and crash into a concrete culvert?

Or did another vehicle try to scare her or run her off the road? We were pretty late in the reporting process for this podcast when we tracked down the bumper of Karen's Honda Civic. And that set this whole accident reconstruction idea in motion.

We scrambled to find someone who could do the work, and ABC News hired Steve Irwin and his team to review all the evidence we could pull together for them.

In this episode, what we learned, how it sits with the family, and where we go from here. From ABC Audio, this is Radioactive, The Karen Silkwood Mystery. Episode 5, The Phantom Vehicle. Our last episode. I'm Mike Boettcher. And I'm Bob Sands. This Zoom call, it's pretty strange when you think about it.

50 years after Karen's death, her three adult children, her two sisters, even one of her granddaughters who never got to meet her, can beam in and watch a guy run computer models simulating the path her car took that night, its velocity, angle, and final moment of impact.

They watch this little digital version of her car smash into a wall on a loop, as if it's backing up and hitting the wall once, twice, three times.

Steve's been in the business for 37 years. He actually worked with A.O. Pipkin back in the 80s, and Pipkin was an important person in Steve's life.

Steve's long-ago work with Pipkin meant something to Pipkin's daughter, Karen Pipkin Guerrero, too. You met her in the last episode when we drove to her home in Albuquerque to see the bumper.

I'm glad. Three generations of Karen's family are here today. Her sisters, Rosemary Silkwood Smith and Linda Silkwood Vincent, along with her son, Michael Meadows. And for the first time, we're joined by Karen's daughters, Christy Riddles and Don Lipsy. Don's 20-year-old daughter Riley is sitting by her mom.

Steve begins with the indisputable facts of the accident. That Karen's car collided with the cement wall of that culvert. The moment of impact. So this is her car. It's taken. He displays a photo of the front end of Karen's tiny white Honda, jagged and crumpled. The hood is collapsed toward the steering wheel like a crushed soda can.

What happened in the moments after the car drove off the road, before it hit the wall? And the question we're all wondering, what caused Karen's car to leave the road in the first place?

Steve and his team looked for signs that Karen might have been trying to regain control after she left the road. Was she steering or braking? He found signs of both.

That would set up the next sequence Steve is looking at. After Karen's car hit the wall and came to a rest, its nose was pointed toward the roadway.

Then there's the question of speed. The speed limit on the highway was 55, and Steve believes it's a reasonable assumption that she was going the speed limit. The alternative would be that she was drowsy or sedated and driving slower than the speed limit. Pipkin calculated by the time Karen hit the wall, she was going 30. Steve says that matches their modeling too.

So the drop in speed after leaving the road to Steve, that indicates the driver took action.

So Karen was awake at the moment of impact. That's the opinion of one expert using the latest in accident reconstruction technology. The idea that Karen was asleep, maybe even in a stupor, as law enforcement once said, that doesn't necessarily check out. And Steve's findings challenge at least one theory that placed the blame for the accident solely on Karen Silkwood.

The Oklahoma Highway Patrol didn't have any comment on the new assessment, and they told us there are no plans to reopen the investigation.

Steve has created simulations of three possible scenarios. In one, the car veers off the road to the right, then overcorrects to the left and loses control.

These are both single-car accidents. But what we've all been waiting for Steve to tell us about is the bumper.