MINEOLA, N.Y. (AP) -- A man convicted of murder in a drunken driving case tried to muddy evidence during his trial by slipping someone else's saliva into his mouth before a DNA test was taken, prosecutors said.

The test was eventually redone, and Martin Heidgen was convicted of killing a wedding limousine driver and a 7-year-old flower girl in a head-on collision. He was to be arraigned Friday on a new charge of tampering with evidence in what Nassau County District Attorney Kathleen Rice called a "deplorable" tactic to thwart justice.

Heidgen was indicted Thursday, after prosecutors said a DNA sample ordered during his trial revealed the presence of not only Heidgen's genetic profile, but that of another inmate incarcerated with him.

In addition to the 18-year sentence he is serving for his conviction on murder, driving while intoxicated and other charges, Heidgen could face an additional four years in prison if convicted of evidence tampering. His attorney, Stephen LaMagna, did not return a telephone call seeking comment Thursday.

Prosecutors said the Long Island man drove the wrong way down a highway after a night of heavy drinking, slamming into the limousine.

He was charged with murder _ a rarity in DWI fatal crashes _ after prosecutors said he showed a "depraved indifference to human life" by ignoring drivers who flashed their headlights and honked their horns as he drove the wrong way into traffic on the Meadowbrook Parkway in July 2005.

LaMagna is appealing the conviction.

Blood taken from the scene and confirmed as Heidgen's revealed the blood-alcohol level to be 0.28, more than three times New York's legal limit of 0.08. Prosecutors estimated Heidgen consumed at least 14 drinks before getting behind the wheel of his pickup truck.

Killed were Katie Flynn and driver Stanley Rabinowitz. Five of the girl's relatives were injured.

Since the crash, Katie's parents, Jennifer and Neil, have advocated for stricter drunken driving laws. They told their story on "The Oprah Winfrey Show" last spring and successfully lobbied lawmakers in Albany to strengthen DWI laws.