Police have identified a suspect in the stabbing death of a Chicago dermatologist in his downtown office last year, according to a report.

The Chicago Sun-Times identified the man as Hans Peterson and said he told the police that he thought the doctor had prescribed an acne medicine that had rendered him impotent.

Chicago police Tuesday didn't release Peterson's name at a news conference because a prosecutor said he hasn't been formally charged, but the Sun-Times identified Peterson from arrest warrants issued in June.

Police said at the press conference that a suspect had turned himself in to French authorities in St. Martin, and was being held on a federal fugitive warrant in connection with the death of 64-year-old Dr. David Cornbleet of Lincolnwood, Ill., found stabbed to death in late October of last year.

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Authorities are working to extradite him from French St. Martin, which shares a Caribbean island with Dutch-controlled St. Maarten.

But extradition from the French-controlled part of the island is "complicated," said Bob Milan, the first assistant Cook County state's attorney. And one issue authorities are looking into is whether the man acquired French citizenship in St. Martin.

If he did, that's "going to make extradition very difficult," said the FBI's William Monroe, assistant special agent in charge.

France, in principle, doesn't extradite French citizens, but the government still is working to determine the citizenship status of the suspect, said Pascale Furlong, a spokeswoman for the French Consulate in Chicago.

Milan said his office will "do everything in our power to bring this individual back here to stand trial in Cook County."

Police have worked for 10 months to try to solve Cornbleet's slaying. He was found stabbed to death inside his Michigan Avenue office.

"Today's news should bring some relief to the Cornbleet family. They can now take comfort in knowing that a suspect has surrendered," said interim Police Supt. Dana Starks.

But Cornbleet's son Jon called the latest development "bittersweet."

"I wish he was here," Jon Cornbleet said of his father.

An arrest warrant for the suspect was issued June 8, but authorities won't say when the man surrendered. They also wouldn't discuss a possible motive.

Authorities thanked the Cornbleet family for helping to keep public attention focused on the case through the news media and by using the social networking site MySpace.com to feature information about the crime. That included surveillance tape images that showed a man — but not a clear image of his face — entering the building that housed Cornbleet's office and then leaving about an hour later.

Police had another security video from a downtown parking garage that depicted the same man seen leaving the office building, Cmdr. Steve Peterson said. Police also had DNA evidence.

Authorities would not discuss what information they got from MySpace that helped in the case, but Peterson said "that started the ball rolling" for the warrant, which was based on DNA.

Peterson said the man also had lived in New York.

The Associated Press contributed to this report.

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