Experts: Marijuana amplifies alcohol's effects

Alcohol's effect: Having twice the legal limit of alcohol can cause people to have difficulties in perception, judgment and memory, said Elizabeth Spratt of the Westchester Laboratory.

Marijuana and alcohol:Adding marijuana - especially if smoked right before the crash - would only enhance the effect of the alcohol, impairing judgment even further, drug and alcohol experts said. "Cannabis augments the intoxication," said Dr. Constantine Ioannou of the Nassau University Medical Center. Severely drunk and high people often have "tunnel vision," Spratt said.

Photos: Latest from the fatal Taconic Crash and reaction

Marijuana's effect: Dr. Jeff Selzer, an addiction psychiatrist at North Shore University Hospital in Manhasset, said studies have found that use of cannabis alone can also significantly impair judgment in driving - especially right after it is used.

It depends on the person: How people react to alcohol and marijuana depends on such factors as personal history of use, ethnic background and drinking pace, Ioannou and Selzer said. Some people would have passed out well before 10 drinks, Ioannou said.