The former “Wyandanch railroad rapist” of the late 1970s was convicted Wednesday of beating his girlfriend to death last year.

Willie Johnson, 60, looked away and snorted when the jury pronounced him guilty of first-degree manslaughter in the death of Thelma Stewart, 49.

She died a few days after what prosecutors said was a severe beating on May 12, 2015, which left her covered in bruises and with a broken jaw, broken nose and ruptured spleen.

Johnson testified last week that Stewart was a severe alcoholic who often fell down and bumped into furniture. He said it was also possible that “crackheads” who lived in the Wyandanch rooming house where he and Stewart lived may have beaten her.

“I’m happy the jury convicted him in this case,” said Assistant District Attorney Raphael Pearl. “Mr. Johnson has a long history of abusing women.” Johnson served 18 years for a series of knife point rapes near the Wyandanch train station.

Johnson faces a maximum of 25 years in prison when Suffolk County Court Judge Barbara Kahn sentences him on Dec. 13 in Riverhead.

“Obviously, Mr. Johnson and I are disappointed with the verdict,” said his attorney, Donald Mates Jr. of Hauppauge. He said an appeal is likely.

First, however, Johnson still faces trial on a charge of not registering as a sex offender.

In his closing argument Monday, Mates reminded jurors that one witness gave a fake name to police when she called 911, another fake name to police when they interviewed her and then disappeared for a day in the middle of her testimony during the weeklong trial.

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Mates said no blood from such a prolonged beating was found in either the bedroom or on Johnson, and there were no marks on his hands at the time of his arrest.

Pearl highlighted the testimony of witnesses in the house who said they heard a beating and moaning. The prosecutor said the victim had extensive bleeding, but most of it was internal, from the ruptured spleen.

The problems of others in the rooming house was irrelevant, and their stories had the ring of truth, Pearl said.

Pearl said if they were lying, they at least could have done a better job and said they saw the attack. He also called attention to what Johnson told police when officers found him: “I didn’t do it! She fell!”

That’s not what an innocent person would say, Pearl told jurors.