UNIONTOWN, Pa. -- The Baby Mary investigation -- an infant girl found dead in a Fayette County creek -- was a cold case for more than eight years and consumed a state trooper who refused to give up on it.

Now, state police have made their second homicide arrest in a two-month span in connection with the June 2000 discovery of that baby girl's body in North Union Township.

WTAE Channel 4's Amber Nicotra reported that Warren Ernest Bircher, 33, was charged with homicide Wednesday. Police had already charged the man's sister-in-law, Sarah Sue Hawk, 25, who they said was the girl's mother.

Bircher and Hawk, of Uniontown, who was 16 at the time, were having an affair when Hawk revealed that she was pregnant by another man, according to police.

After Hawk gave birth, Bircher gathered some plastic bags, a flannel shirt and a backpack, and put the child inside the bag and took the backpack to Cove Run Creek, police said.

The loss of the infant no one claimed they knew forced the coroner to name her Baby Mary.

In November, Pennsylvania State Police said results of an analysis by the New Jersey State Police Mitochondrial DNA Laboratory and a maternity style analysis by the Marshall University Forensic Science Center in Huntington, W.Va., showed that Hawk was the mother. Armed with that new information, police were able to arrest Hawk. A witness reported hearing Hawk that Bircher admitted to her that he put the baby in the creek.

Police also heard from a witness who told them that, during a party, Bircher talked about how he would get rid of the baby.

"Bircher said he was going to put the child in a bag and drown it just like he does his animals because she doesn't have the nerve to do it and he cannot afford another child," a witness said, according to a police affidavit.

Bircher has pleaded not guilty and is being held in the county prison. He and Hawk each have court appearances scheduled next week.

Trooper James Pierce, who stayed on the case from the beginning, said he doesn't believe arrests would have been made had forensic experts not been able to find a link between the mother and baby.