A Common Pleas judge yesterday convicted a 22-year-old North Philadelphia man of third- degree murder for beating a younger friend to death this spring and leaving his body rotting in a closet for weeks, authorities said.

Nicholas Lux, of Master Street near Hancock, is to be sentenced by Judge Jeffrey Minehart on Jan. 31.

Lux faced what's called a degree-of-guilt hearing. He pleaded guilty Monday to "homicide generally" in the slaying of Arthur "Arty" Miller, 18, Lux's attorney, Edward Reif, said yesterday.

During the hearing yesterday and Monday, both sides presented witnesses. Then, it was up to the judge to determine what Lux should be convicted of - first- or third-degree murder, or voluntary manslaughter.

At the hearing, Joseph "Fester" Grone, Miller's cousin, testified that he found Miller's body, streaming with maggots, on May 12 in Lux's home.

Lux, then 21, had covered Miller's body with three or four trash bags and stuffed him into a large storage bin, which was placed in Lux's bedroom closet, Assistant District Attorney Leon Goodman said yesterday after the hearing.

Gregory McDonald, an assistant medical examiner, testified that "Arty had been dead for approximately two weeks," the prosecutor said.

McDonald also testified that the evidence showed that Lux had "struck Mr. Miller seven times in the head; once in the jaw, fracturing his mandible; and once in the hand" with a rebar or iron bar, the prosecutor said.

Lux took the stand yesterday and testified that Miller had been living at his house at the time. But then his mother didn't want Miller there, and the two friends got into an argument, Lux said.

Lux testified that Miller had made some disparaging remarks about his [Lux's] mother and grandmother. He also said Miller had tried to attack him with a knife.

Prosecutor Goodman contended Lux's story about the knife attack was false.

Miller's mother, Princessa Miller, 42, who attended the hearing, said last night by phone that she was "very upset" that the judge had found Lux guilty of third-degree, not first-degree murder.

"After the first hit, it was murder, it was intent to kill," she said.

"What made [the judge] decide that way? Maybe because he [Lux] pleaded guilty? Or maybe because he's a kid?" she wondered.

Julie Grantano, Miller's aunt, also expressed disbelief that the judge had found Lux guilty of third-degree. *