Upper Darby police were searching yesterday for a man accused of beating his 3-month-old son, causing brain damage that could be permanent.

Henry Paris III, 32, of the 3700 block of Taylor Avenue in Drexel Hill, fled Thursday night in a white Nissan sedan bearing Pennsylvania tag GWK-2718. He is wanted on charges including aggravated assault and endangering the welfare of a child, and could face up to 20 years in prison, said Police Superintendent Michael J. Chitwood.

Police believe Paris may have fled to New York City, where he has friends.

Paris' son, Henry Paris IV, suffered a skull fracture and three broken ribs, injuries consistent with blunt force trauma, according to a police affidavit. The child had been upgraded to stable condition yesterday at Children's Hospital of Philadelphia, but after nearly two weeks there, his prognosis is not good, Chitwood said.

"Due to the significance of the injuries . . . we suspect that he will be dependent on others for the rest of his life," Chitwood said at a news conference yesterday.

The child was rushed to the hospital on the night of Nov. 24. He had been crying, but when the babysitter tried to feed him, his eyes rolled back, and his body tensed and then went limp, according to the affidavit.

A doctor at Children's Hospital said that the left side of the baby's skull had been fractured and that a large amount of blood had pooled around his brain. His ribs were broken as if someone had squeezed him, according to the affidavit.

When questioned by police Nov. 26, Paris said his son sometimes cried for 30 minutes at a time. It was frustrating, he said, and he sometimes put the baby on his lap until he "chilled," according to the affidavit.

Two former coworkers told police that Paris had a quick temper. Records show he is awaiting trial in Philadelphia on bookmaking charges.

The baby's mother, Naz Alvi, told police yesterday that Paris had said he was unfit to be a father because he could not console his son. She also told police that Paris had "raised his hand to her on past occasions," according to the affidavit.

Paris telephoned Alvi and a friend early yesterday and said he had accidently dropped his son when he was drunk sometime in the last month. He told Alvi he had fled and was far away at a hotel.

Paris asked his friend, Eliot Garney of New York, to look after his family. He said he was sorry about what had happened to his son and was thinking of "ending it all," according to the affidavit.