Legal experts across the country are debating the effectiveness of something called "retrograde extrapolation."
It's used mostly in drunken-driving cases to estimate the level of a person's intoxication, usually when they are arrested hours after a car crash.
A Long Island prosecutor is using it to prosecute a man accused in a fiery crash that killed a father and his two young children. Although the driver had a blood-alcohol reading below the legal limit when he was arrested, authorities claim he was well over the limit when the crash occurred.
The driver's attorney and drunken-driving experts around the country contend the extrapolation is an unreliable measure of a person's intoxication.
Some states require prosecutors to merely use the blood-alcohol readings taken at the time of a person's arrest.
