Karen Pipkin Guerrero

Fagan believed the dents could have been caused after the crash when the car was dragged out of the ditch by a tow truck driver. The bumper could have hit one of the concrete retaining walls.

Fagan believed the dents could have been caused after the crash when the car was dragged out of the ditch by a tow truck driver. The bumper could have hit one of the concrete retaining walls.

And he thought other evidence suggested the presence of another car, too. When he examined the tire tracks Karen's car left in the muddy grass, he thought they suggested Karen had lost control of the car before it ever left the road. The car was rotating instead of tracking in a straight line.

And he thought other evidence suggested the presence of another car, too. When he examined the tire tracks Karen's car left in the muddy grass, he thought they suggested Karen had lost control of the car before it ever left the road. The car was rotating instead of tracking in a straight line.

And Pipkin wrote in his report that suggested, quote, either an impact by an unknown vehicle or a combination of an impact by an unknown vehicle and then driver overreaction and subsequent loss of control.

And Pipkin wrote in his report that suggested, quote, either an impact by an unknown vehicle or a combination of an impact by an unknown vehicle and then driver overreaction and subsequent loss of control.

Karen wasn't asleep. Pipkin's finding was explosive.

Karen wasn't asleep. Pipkin's finding was explosive.

Now, Oklahoma law enforcement and Kerr-McGee were the ones being looked at under a microscope. A higher-up in the Highway Patrol was assigned to reinvestigate the crash, a guy named Lieutenant Larry Owen. He doubled down on the conclusion that this was a one-car accident. And in January 1975, about two months after Karen's death, he also added a new detail.

Now, Oklahoma law enforcement and Kerr-McGee were the ones being looked at under a microscope. A higher-up in the Highway Patrol was assigned to reinvestigate the crash, a guy named Lieutenant Larry Owen. He doubled down on the conclusion that this was a one-car accident. And in January 1975, about two months after Karen's death, he also added a new detail.

Karen had been under the influence of drugs that night. Here's Owen in an interview with ABC.

Karen had been under the influence of drugs that night. Here's Owen in an interview with ABC.

And these co-workers both allegedly told Fagan they'd offered to drive her home that night.

And these co-workers both allegedly told Fagan they'd offered to drive her home that night.

In a 1980 interview for a documentary about the nuclear industry, Jean Young described her recollection of Karen as they were leaving the union meeting.

In a 1980 interview for a documentary about the nuclear industry, Jean Young described her recollection of Karen as they were leaving the union meeting.

A toxicologist we spoke with said we can't draw any conclusions about what the levels found in her body might have meant. There are too many unknowns, like whether Karen had developed a tolerance for the medication. Reporters also question other elements of the Highway Patrol's investigation. Here's NPR's Barbara Newman talking to Lieutenant Larry Owen about why he hadn't inspected Karen's car.

A toxicologist we spoke with said we can't draw any conclusions about what the levels found in her body might have meant. There are too many unknowns, like whether Karen had developed a tolerance for the medication. Reporters also question other elements of the Highway Patrol's investigation. Here's NPR's Barbara Newman talking to Lieutenant Larry Owen about why he hadn't inspected Karen's car.

We reached out to the Oklahoma State Highway Patrol about their investigation, but they didn't have any comment. But I was able to get Larry Owen on the phone. He's retired now, but stands by his conclusion that Karen Silkwood fell asleep at the wheel. He said that nothing had changed in 50 years. Last month, he spoke about his investigation with KOCO, a local television station in Oklahoma.

We reached out to the Oklahoma State Highway Patrol about their investigation, but they didn't have any comment. But I was able to get Larry Owen on the phone. He's retired now, but stands by his conclusion that Karen Silkwood fell asleep at the wheel. He said that nothing had changed in 50 years. Last month, he spoke about his investigation with KOCO, a local television station in Oklahoma.