The puzzle of Roman Polanski, a filmmaking genius and a wildly neurotic individual, is not solved in the fascinating documentary “Roman Polanski: Wanted and Desired.” But one notorious incident in Polanski’s life is illuminated.

While taking photographs for a magazine shoot in 1977, Polanski had “unlawful sexual intercourse with a minor” (the exact charge he later pleaded guilty to), the victim being the 13-year-old subject of the photographs.

He was quickly arrested for this crime, but the movie is concerned with what happened next. The media circus that followed, the movie convincingly argues, influenced the behavior of the eccentric judge in the case, Laurence Rittenband.

Relying on many interviews but particularly on extensive information from Polanski’s attorney, Douglas Dalton, and District Attorney Roger Gunson, the film builds a portrait of justice gone bad. The judge appears to have been more concerned with the appearance of things than the proper protocols of the case.

Without going into too much detail, suffice it to say that today, Gunson — who, after all, was prosecuting Polanski for child rape — says he can understand why Polanski would flee to Europe, given the judge’s untrustworthy behavior (Polanski had already served time for the crime, although the official recommendations were for probation).

Polanski left the United States in 1978 with final sentencing still pending, and has never returned. His victim is interviewed in the film, and she seems as weary of the case as anybody else.

Director Marina Zenovich does a skillful job of suggesting why Polanski would not have much trust in a system of justice. His mother was murdered in the Holocaust, he was raised in Communist-controlled Poland, and his wife, actress Sharon Tate, was killed by the Manson family.

The behavior of the press in the wake of the Manson killings included free speculation that Polanski, who made weird movies and had a colorful lifestyle, might well have been involved in the murders. When the truth about Manson came out, it hardly erased the aura of depravity that had been created around Polanski.

The spectacle of a never-ending legal nightmare must have seemed like something out of Kafka … or a Roman Polanski movie. The lucid paranoia of Polanski’s movies was re-creating itself in a Los Angeles courtroom.

None of this exonerates Polanski, or excuses his crime. It’s possible the movie doesn’t say that often enough, and Zenovich does seem more concerned with the strangeness of the court case than with the fallout for Polanski’s victim. But the court case is the subject of this film.

One of the haunting things about this movie is the way Polanski’s world view, so eloquently expressed in “Chinatown” and “Knife in the Water” and “Rosemary’s Baby,” was confirmed by events in his own life. On that subject, there’s room for more documentary films.