A Pennsylvania couple in the city of York went on trial Tuesday for the death of their adopted Russian son.

Michael and Nanette Craver have been in jail without bail since they were arrested last year and charged with homicide in the death of 7-year-old Russian-born Nathaniel.

He died in a hospital after the Cravers found him lying in bed, unresponsive.

Prosecutors accuse the couple of beating and abusing the child. Doctors say the boy's body was covered with layers of bruises and cuts and that he had brain damage. One nurse described his head as being like a wet sponge.

The Cravers' lawyers argue that Nathaniel was born with an illness that triggered severe behavioral problems, causing him to constantly injure himself. The Cravers say Nathaniel purposely smashed his head against a stove and threw himself down the stairs.

Russian authorities are closely watching the case. It comes after Moscow and the United States signed a treaty in July regulating adoptions of Russian children by American families.

Under the treaty, U.S. couples must undergo psychological exams by Russian authorities, who also have the right to monitor Russian children in their new families.

Russian officials had threatened to suspend U.S. adoptions after reports of child abuse by their American families. In one case that made headlines last year, a woman in Tennessee put her adopted Russian son on a plane back to Moscow alone, saying she could no longer cope with his violent behavior.