Driven To Extremes

48 Hours Mystery Tracks A Mother Charged With Manslaughter In Car Crash

(CBS)  The jury hears nothing from Dennis about his bitter separation from Mary, or allegations of physical abuse. And Dennis tells the jury that Mary was in a very good mood just hours before the accident.

Suffering from a stomach ailment, Mary was forced to leave the courtroom. During her recovery, the jurors take a field trip to the site of the crash, to see firsthand where Amy and Carrie died.

The defense team relies on a British electrical engineer to convince the jury that the accident wasn’t Mary’s fault, but rather a fault in her BMW. The engineer, Dr. Antony Anderson, testifies that the reason for the accident was “a sudden acceleration event” caused by what he claims is “a rogue electrical signal.”

“A rogue signal can come in and give a false command … which can affect these very sensitive electronic circuits within the cruise control,” says Anderson, who believes this false command could have switched on the BMW’s cruise control, triggered the accelerator and caused the car to speed up on its own.

But the prosecution’s BMW expert, Mark Yeldham, twice tested Mary’s BMW and found “no faults stored in the cruise control system.”

Yeldham, who works for BMW, admits the company receives dozens of sudden acceleration complaints every year. But of those 50 complaints each year, Yeldham says most involve driver error.

In a final move to bolster their runaway car argument, the defense calls two drivers who claim their BMWs had also experienced sudden acceleration.

And on the last day of the trial, after three and a half years of silence, Mary is called to take the stand. Incredibly, it was the first time Brown and prosecutors have heard from Mary about the crash.

“It picked up speed. It started going faster. I released the brake and applied it again,” says Mary. “The car started to go out of the lane, it was fishtailing. Everything was very quiet, and I remember looking down at the dash, and said ‘Why won’t you stop?’”

After five days of testimony, it was up to the jury to decide Mary’s fate.
If found guilty, Mary could spend the next 30 years behind bars. After just five hours, the wait was over.

The jury found Mary guilty on all counts, a dramatic rejection of her claim that her BMW had sped out of control on its own, killing Amy and Carrie, and causing brain damage to their friend, Zak Rockwell.

“I prayed and hoped that justice would come, and it came today,” said Carrie's mother, Rita Brown.

Mary will remain free on bond until sentencing, but she is ordered to hand over her driver’s license. As reporters mob her, Mary is too distraught to talk.

But Heather and Julie Hill, Dennis’ daughters from his first marriage, have plenty to say. They contacted 48 Hours after the trial, with explosive allegations the jury never heard.

They say they know what it’s like to be in the back seat of a speeding car driven by Mary. “She got mad at my dad and she tore down the highway going like 90 miles an hour. I remember I was so scared in the back seat,” says Julie.

“They’re angry at me over Amy’s death. I’m not their mother; I’m their stepmother,” says Mary. “Truthfully, if I go to jail, let’s face it, it will help their father considerably with the divorce.”

And it's jail time that Brown pleads for at Mary's sentencing: "Carrie will not go off to college. I will not be able to spoil her children. I will not be able to take care of them when she's on vacation with her husband, the husband she never met."

For the first time since the accident, Mary utters the words Brown has waited so long to hear: “The words 'I’m sorry' can never convey to her how I feel. I do apologize to the parents and to the families and to the friends and to everyone that knew Carrie and Amy and Zack."

“I felt like she meant it, but it’s too little too late, I guess,” adds Zak.

The judge then surprises everyone by ordering Mary to jail until he decides on her sentence. Even her estranged husband, Dennis, finds the sight of her in handcuffs unbearable.

“It’s probably one of the worst moments I’ve ever gone through in my life. It hurt a lot, it really did,” says Dennis. “I just think that she will just will herself to die and she’ll just die in jail, and I don’t know if I can really handle that.”

More than three months later, a visibly shaking Mary Hill, now being treated for depression and alcohol and drug addiction, is back in court to hear the judge's decision. She was sentenced to serve 15 years in the Department of Corrections in Florida.

Mary received the sentence with some advice from Judge O.H. Eaton: "Mary Hill, I don't know what you're gonna go with your life. You're going to have to make a lot of adjustments."

Mary once had it all: a successful business, a mansion where she raised a loving family, and a world of possibilities. But now, a prison will be the only world Mary will know until she's almost 70.

But will the tragedy ever truly be over for any of the survivors? Mary and Dennis are getting a divorce.

Kaitlin is still in custody of her older sister, and must deal with the haunting memory of her mother in shackles. And Rita Brown can only dream of what her daughter, Carrie, might have become.

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After the trial, two new witnesses came forward claiming Mary Hill was not speeding just before the crash.

Despite their testimony, the judge denied Hill's request for a new trial. She's filing an appeal.

After serving 10 months in prison, Mary Hill was released on a $50,000 bond pending the outcome of her appeal.