A judge sentenced the man who calls himself Clark Rockefeller to four to five years in prison for kidnapping his 7-year-old daughter during a supervised visit in Boston.

The German-born Rockefeller — whose real name is Christian Karl Gerhartsreiter — also was sentenced Friday to two to three years for assaulting a social worker, but that will run concurrently to the time he'll serve for the little girl's abduction.

The sentence was considered light. The judge said he took into account that Gerhartsreiter, 48, was a first-time offender and a genuinely distraught father, but also weighed his history of deceptive behavior, his rough treatment of the social worker and the fact that he put his daughter Reigh's life in danger.

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The conviction on assault and battery with a dangerous weapon carried a maximum of 10 years in prison, while the parental kidnapping charge carried a maximum of five years.

Earlier Friday, Gerhartsreiter was convicted of one count of kidnapping and one count of assault. He was acquitted of another assault count and of a charge of giving a false name to police.

Gerhartsreiter spun fantastic stories about himself during three decades in the United States, including a tale that he was a member of the elite, wealthy Rockefeller family.

He snatched Reigh during a supervised visit last July after losing custody of her to his ex-wife. He also was charged with two counts of assault on a social worker.

Jurors reached a verdict on their fifth day of deliberations in the case. Earlier in the week, they had asked the judge for more explanation on the insanity defense.

The jurors, who began deliberating Monday, rejected the theory put forth by Gerhartsreiter's lawyers: that he was suffering from a delusional disorder and was legally insane.

Prosecutors called the diagnosis "preposterous" and said he planned the kidnapping for months because he was angry that his wife had divorced him and gained custody of their daughter, Reigh.

Gerhartsreiter, wearing a dark suit and red-striped tie, looked sober but calm as the verdict was read. He had clasped his hands as he awaited the seating of the jury.

Gerhartsreiter also was convicted of assault and battery with a dangerous weapon for ordering the driver of an SUV to pull away with a social worker clinging to the door.

District Attorney Daniel Conley called the verdict "fair and just" and said hoped it gives Gerhartsreiter's ex-wife Sandra Boss and her daughter "some sense of justice."

"This was a difficult ordeal for this family to endure," Conley said.

Defense attorney Jeffrey Denner expressed disappointment, but said: "It was a very fair trial and the jury considered the case very carefully. We can ask for no more.

"We got two out of four not guiltys," Denner said. "We would have preferred four."

Denner said his client had a "flat" reaction to the verdict and did not say much. "I think he was probably grateful he was found not guilty on some of the charges and disappointed he was found guilty on some of the other charges," the attorney said.

Jurors appeared sober and tense as the verdict was delivered. They later returned to the courtroom and foreman Michael Gregory, a Harvard Law School lecturer who specializes in the impact of domestic violence on children's learning, read a statement saying they are "confident that our verdict is fair and just and based on the information that we were legally allowed to consider." The statement said, "All of us stand by the verdict completely."

After his arrest, authorities revealed that the man with the storied Rockefeller name was really a German national who had used multiple aliases since moving to the United States and was a "person of interest" in the 1985 disappearance and presumed slayings of a newlywed couple from San Marino, Calif.

A California grand jury has been hearing evidence in the disappearance of Linda and Jonathan Sohus. Gerhartsreiter, who was then using the name Christopher Chichester, was living in a guest house on their property when they disappeared. He has not been charged in the case.

The kidnapping trial featured incredible details about the many personas Gerhartsreiter assumed as he worked his way into wealthy circles in Boston, New York and Los Angeles.

He came to the United States in 1978 as a 17-year-old student in Connecticut, and three years later, persuaded a woman in Wisconsin to marry him so he could get a green card.

After that, he told a variety of stories: he was a physicist, a financial adviser who renegotiated debt for small countries, a collector who owned $1 billion worth of modern art, a cardiovascular surgeon from Las Vegas, a ship's captain based in Chile and a member of the Trilateral Commission, a group established to foster cooperation among the United States, Europe and Japan.

Boss, a Harvard-educated management consulting firm executive, testified that she believed her husband's stories for much of their 12-year marriage. It was only when she hired a private investigator during their 2007 divorce that she realized he "was not the person he'd said he was," she said.

She testified that he asked for a $1 million divorce settlement, which was later negotiated down to $800,000. Boss was awarded full custody of their daughter. As part of the agreement, he was allowed to see his daughter three times a year in visits supervised by a social worker.

It was during the first visit that he snatched the girl.

Social worker Howard Yaffe testified that Gerhartsreiter pushed him to the ground and hustled his daughter into a waiting SUV, then told the driver to "Go! Go! Go!" Yaffe said he tried to climb into the car to stop him from taking the girl, and tumbled to the ground again as the SUV pulled away.

Father and daughter were found in Baltimore six days later. The girl was returned to her mother in London.

A Baltimore real estate agent testified that Gerhartsreiter contacted her months before the kidnapping and, identifying himself as a ship's captain, asked for help finding a house where he and his daughter could live. The week before the kidnapping, he bought one for $450,000. The agent tipped off authorities after seeing his photo on news reports.

Denner, the defense attorney, told jurors that Gerhartsreiter had been mentally ill for years, but suffered a psychotic break after he lost custody. He said Gerhartsreiter believed he was communicating telepathically with his daughter, who was telling him she was in danger.

Two mental health experts testified that they diagnosed Gerhartsreiter with a delusional disorder and narcissistic personality disorder — illnesses they said made him unable to understand right from wrong.

Assistant District Attorney David Deakin said Gerhartsreiter had become accustomed to a lavish lifestyle, funded by Boss, and was angry about the divorce and loss of custody.

"This is not a case about madness," Deakin said. "It's a case about manipulation."

• Partial List of Witnesses at the 'Clark Rockefeller' Trial

Click here to read more on this story from MyFOXBoston.com.

The Associated Press contributed to this report.