A Prince George's County Circuit Court judge has dismissed all charges against Thomas V. Hinley, the 48-year-old Upper Marlboro man accused of setting a fire that killed his elderly parents last spring.

Judge Samuel W. H. Meloy dismissed the murder charges Wednesday, according to a spokesman for the county state's attorney's office, saying the prosecution had failed to prove beyond a reasonable doubt that Hinley had set the fire. The judge also ruled that a statement made by Hinley was inadmissible as evidence because it had been obtained under duress.

Vance A. Hinley, 72, and his wife Catherine, 66, died in the blaze last May 16 that destroyed their home at 9527 Montrose St., Upper Marlboro.

When first officials arrived, they found the bodies of Mr. and Mrs. Hinley hudled together on an upstairs floor. Thomas Hinley who received minor burns had escaped, fire officials said.

According to Assistant State's Attorney Robert J. Matty, the prosecution tried to show that Hinley had used gasoline to start the blaze on the living room sofa and in an upstairs closet. Matty said Hinley contended his mother had set the blaze.

The judge's ruling ended a three day jury trial.