The 16-year-old son of a Long Island Rail Road executive has been sentenced to three to nine years in prison for robbing and seriously injuring Mary Trump, the mother of Donald J. Trump, on a street near her Queens home.

The sentence, which was imposed Friday on Paul LoCasto, prompted the youth's lawyer to charged that his client had received a harsher punishment than he would have if the victim had not been "high profile."

Mr. LoCasto pleaded guilty last month to assault and robbery for throwing the 79-year-old woman to the ground last October while grabbing her pocketbook at Union Turnpike and 177th Street, near her Jamaica Estates home. She suffered a brain hemorrhage, several fractures and permanent damage to her sight and hearing, an assistant district attorney, David Dikman, told Justice Arthur J. Cooperman in State Supreme Court in Queens.

Mr. LoCasto's lawyer, Bernard R. McConville, had urged a sentence involving no imprisonment but alcohol-abuse treatment, saying his client had no criminal record and was a teen-age alcoholic who had been drunk during the crime. But Justice Cooperman termed the crime "violent and serious."