ALBUQUERQUE, N.M. (AP) - A man accused of beating a pregnant woman to death also is being prosecuted under a 2004 federal law that makes it a separate crime to kill a fetus while causing the death or injury of the mother.

It might be the first time the Unborn Victims of Violence Act signed by President Bush has been used. U.S. Attorney Greg Fouratt said his office's research found "no other case in the country in which that section (of law) has been charged," the Albuquerque Journal reported Tuesday.

Defense attorneys for Frederick Beach said they expect to pursue any available legal challenges.

"We may be breaking ground on a new area of law," said defense attorney Amy Sirignano. "We're not sure where that will lead us."

Beach, 37, pleaded not guilty last month to killing a fetus and to first-degree murder and child-abuse charges.

He is accused of beating to death Verlinda Kinsel, 29, in September and killing the fetus she had said was his. Authorities say the victim's 9-year-old son witnessed the assault.

If convicted, Beach faces life in prison.

The case is being prosecuted in federal court because Kinsel was killed on the Navajo reservation.

The Unborn Victims of Violence Act stemmed from the abduction and murder of a pregnant woman, Laci Peterson, in California in 2003. The law makes it a crime to kill a fetus in utero at any stage of development while committing another federal crime; it does not require that the perpetrator knows the woman was pregnant. The law covers activities defined as federal crimes, including kidnappings, bombings, drug trafficking and crimes on federal and tribal lands.

Navajo police in Crownpoint got a call Sept. 17 about a woman lying next to a car west of Gallup. Kinsel was taken to the Gallup Indian Medical Center, where she was pronounced dead.

According to a criminal complaint, Beach walked into the detention center in the Navajo capital of Window Rock, Ariz., and asked to turn himself in for battering his girlfriend.

The complaint said Beach and Kinsel, both Navajos, had been in a sporadic relationship since 2005, and Kinsel had approached him in an effort at reconciliation, telling him she was pregnant with his child.

The two got into an argument when he encountered her while driving to Gallup. He pulled her to the ground and kicked her repeatedly, and hit her on the head numerous times with an aluminum baseball bat he took from his car, the complaint said.