So many misconceptions have been floating around about Alan Dershowitz that its hard to know where to begin.

Accusation: He will blindly defend Israel against any criticism whatsoever.

Actually, he has written about (for example) “the misguided continued occupation and the wrong-headed expansion of settlements.”

Another accusation: He will defend anyone – so long as he gets a huge fee.

Actually, he turns down lots of potential clients – professional criminals, such as drug dealers and gang leaders. And he takes on about half his cases on a pro-bono basis (no fee).

Other things you may not know about Dershowitz:

He helped John Lennon avoid deportation – on charges of using marijuana – in 1975. (His fee: a record album signed by Lennon. Alas, it was lost.)

He declined to represent the man who killed Lennon: “I didn’t feel comfortable helping a defendant who had killed my former client.” He also declined to defend Yigal Amir, accused of assassinating Yitzhak Rabin, prime minister of Israel. One reason: He deeply admired Rabin.

He discouraged Frank Sinatra from hiring him to bring suit against Kitty Kelley, who had written an unflattering book about the singer.

Norman Mailer, the late novelist, asked Dershowitz to represent Jack Henry Abbott, who was serving time for murder – and who became a best-selling author. Dershowitz once asked Abbott whether he had snitched on other prisoners, as was rumored. Abbott leaped across the table and grabbed Dershowitz by the neck. The guards rescued him, but his last words to Abbott were: “No way I’m becoming your lawyer!”

He was consulted by the lawyers for Edward Kennedy after the Massachusetts senator drove his car off a bridge on the island of Chappaquiddick, resulting in the death of a young woman. If the full truth were to be known, he has written, “it would not tarnish the senator’s well-deserved reputation as one of the great political figures of the last half century.” (Later, he worked closely with Senator Kennedy on various legal matters.)

He helped represent O.J. Simpson, who never paid his fee.

He also was consulted about Angela Davis, a leader of the American Communist Party, when she was charged with being an accessory to murder in connection with a shootout at a courthouse. Years later, while she was visiting the Soviet Union, Dershowitz wrote to ask if she would help a list of (mainly) Jewish Soviet prisoners. Some were charged with trying to immigrate to Israel. Davis’s secretary called back to say that the people on the list weren’t political prisoners: “They are all Zionist fascist opponents of socialism.”

Yes, he has lost cases. He was the appellate lawyer for Mike Tyson in his prosecution for rape, suggesting that the young woman who had accused him had been out for money.

It’s interesting how Tyson chose him as his lawyer. When Dershowitz met with him, Tyson asked: “What do you think of me?” Replied Dershowitz, “If you’re innocent, you’re a schmuck.” For visiting a woman in a hotel at 2 in the morning without any witnesses, a woman who could accuse him of rape. Tyson turned to his entourage and said, “This man’s calling me a schmuck. He’s right. I want to know why you guys didn’t call me a schmuck. He’s hired. I need somebody who’s willing to call me a schmuck when I am a schmuck.”

The judge in the case seems to been blatantly biased against Tyson; she refused to admit exculpatory evidence. An appeal was turned down. In his career, Dershowitz has written, he has never seen a “less fair trial and appeal than that accorded Mike Tyson.”

Among the other people whose defense he joined: Michael Milken, the money manager who went to prison; Patty Hearst, the kidnapped heiress convicted of bank robbery and using a firearm in a felony; Claus von Bulow, accused of murdering his wife, Sunny; Mia Farrow against a lawsuit brought by Woody Allen; Leona Helmsley, the real-estate tycoon, who (he has written) “was boring and rather stupid,” and Natan Sharansky, a Soviet dissident arrested in the Soviet Union in 1977 on charges of spying for the United States. (Dershowitz may have saved Sharansky’s life.)

Born in Brooklyn 76 years ago, Dershowitz graduated from Brooklyn College, then from Yale Law School, where he was first in his class. He joined the faculty of Harvard Law School and in 1967 became, at 28, the youngest full professor in Harvard Law’s history. He retired from Harvard in 2013.

Dershowitz has a good sense of humor, too – which helps account for the fact that a few of his many books, like “Chutzpah,” have been best-sellers.

He’s a a secular Jew, but he and his family observe Jewish holidays.

At one time he defended the preacher Jim Bakker, and in gratitude Bakker’s then wife, Tammy Faye, sent him a Passover Haggadah. It had been written, as it turned out, for use at seders conducted by Jews for Jesus.

At a Dershowitz seder, he mischievously had one guest solemnly read from Faye’s Haggadah: “This is the bread of affliction that the people of Israel had to eat when they fled from Egypt.” Then the reader continued: “The holes in the matzoh represent the wounds on the body of our Savior, Jesus Christ, who in his body was punctured during his crucifixion.”

The seder was delayed for quite a long time, derailed by hysterical laughter.