"I never expected it," says Mary. "Not for the most fleeting second could I think that someone would think that I would do something like that intentionally."
Now, Mary and Dennis Hill are fighting back. "We've endured our share, and it's time to turn the tables now. I believe that we're gonna be ready," says Dennis, who has hired high-priced defense attorney Gerald Boyle, best known for defending killer Jeffrey Dahmer, to prove his wife did not intentionally kill their daughter and her friend.
"Mary was an exceptional driver," says Dennis. "I never quite understood how this could possibly happen."
But defense experts think they have an answer. After examining the BMW, they believe a fault in the BMW's cruise control caused the car to speed up on its own.
"Once the investigators were able to say 'Hey there's a problem with the cruise control here. The throttle linkage,'" says Dennis. "Well then, pieces of the puzzle started to go together."
BMW owner Larry Gustafson has never met Mary, but he knows what it's like to have a car suddenly race off.
"The first time it happened to me, I had no idea what was going on," says Gustafson. "It went from 35 to 40 miles an hour to almost 60 miles an hour, just that quick."
Gustafson claims his mechanic fixed the problem on his used BMW by replacing an electrical circuit. But Carrie's mother isn't buying it.
"Mary Hill needs to be held accountable for her actions. And if that includes going to jail, then so be it. The judge and jury will decide," says Brown, who believes that Mary is to blame for Carrie's death.
Both mothers are unable to share their grief over the loss of their daughters, Amy and Carrie, for the battle lines have been drawn.
Mary, charged with vehicular homicide and manslaughter, has become a recluse.
"For over two years, I wouldn't leave this home," she says.
Making things difficult were the rumors flying furiously through their posh Florida community, rumors that Mary had a history of depression, drug use, and dangerous driving.
Sworn statements by Deane David, the Hills' former nanny, fueled those rumors. "I know that something like this was going to happen," says David. "She was a horrible mother. … That was my worst fear, was her in the car with them."
"She has accused me of horrible things," says Mary of David, who worked for the Hills for less than year, and left after a falling out over pay six months before the accident.
David's most scathing allegation was that Mary abused cocaine. "Two weeks into the job, I found out that Mary had a cocaine addiction," says David. "Her purse had fallen off the counter, and in that, a compact had fallen out with powder on the mirror and a razor blade."
But Mary denies these allegations: "I have tried it. I will not say I haven't tried it. But no, I never had an addiction. I don't think trying it once makes you an addict."