PHILADELPHIA (AP) _ A Lehigh County man who three years ago cooperated with police to apprehend his brother on murder charges sued state police, saying troopers broke their promise not to open fire in the arrest.

Keith Heinly of Wescosville was shot once in the neck by police and his brother Kevin fatally shot himself after the gunfire, according to a lawsuit filed Monday in U.S. District Court.

Police ''explicitly promised'' not to shoot at Kevin Heinly and to make every reasonable effort to capture him alive, his brother said.

The suit names state police Commissioner Robert M. Sharpe, Capt. Robert G. Werts and nine unidentified troopers assigned to the Bethlehem barracks. Police have withheld the troopers' names.

Kevin Heinly shot to death Deanna Renner on Oct. 22, 1989, the suit said.

Keith Heinly told police his brother was hiding in their father's house and provided them with a map layout of the inside. That afternoon he went to the house to convince his brother to surrender and not to commit suicide, according to the suit.

The brothers left the house after a ''second volley of shots'' and Kevin Heinly shot himself, the suit said.

Keith Heinly said one of the troopers' gunshots hit him in the neck, causing ''serious and permanent physical and psychological injury.''

He said he was trying to comfort his dying brother when police handcuffed Kevin Heinly and took both brothers into custody.

Keith Heinly claimed police used excessive force and arrested him without probable cause.

He said the troopers lied to the press and their superiors, saying police fired no shots.

Keith Heinly is seeking damages in excess of $50,000 and court costs.

Neither his attorney, Richard J. Orloski, nor State Police Public Information Officer La-Verna Fountain immediately returned calls placed to their offices.

P-DS-10-23-91 0501EDT