Despite pleas from his family and fellow scientists, former Yale geology professor Antonio C. Lasaga was sentenced in state court Friday to 20 years in prison for molesting a New Haven boy he was mentoring.

The majority of Lasaga’s state sentence will run concurrently with the federal sentence of 15 years he received earlier last week for possession and receipt of child pornography.

The testimony from the two sides during Friday’s hearing painted remarkably different portraits of the former Saybrook College master, who did not speak during the proceedings. Lasaga’s ex-wife and son described his warmth and compassion as a father, and his colleagues pointed out his exceptional scientific contributions.

But ultimately Superior Court Judge Roland D. Fasano seemed to side with state prosecutor David Strollo, who compared Lasaga to “the devil incarnate” and cast him as a cold, calculating rapist.

“I am convinced he’s a pedophile and a danger to the community,” Fasano said.

Lasaga pleaded no contest last month to two counts each of sexual assault, employing a minor in an obscene performance, and risk of injury to a minor. In addition to his 20-year sentence, Lasaga must undergo 10 years of special parole, including registration as a sex offender and mandatory counseling.

His attorney, Diane Polan, called the ruling “effectively a death sentence for a 52-year-old man like Mr. Lasaga.”

At the start of the hearing, Strollo told the court that the abuse Lasaga inflicted on the boy was not, as the defense counsel had maintained, a series of mere indiscretions. He said Lasaga hand-picked his victim by requesting a young boy to mentor through a program run by the New Haven public schools and then proceeded to shower his family with gifts to obtain their trust.

Prosecutors have said Lasaga molested the boy over the course of more than five years, and Strollo said Friday that Lasaga took advantage of his role to do damage to the youth that cannot be undone.

“His actions have murdered the mind of a young child,” Strollo said. “The victim lives every day haunted by the abuse suffered at the defendant’s hands.”

Strollo proceeded to describe some of 150,000 pornographic images confiscated from Yale computers to which Lasaga had access.

But while Strollo emphasized the danger the former professor posed, three of Lasaga’s colleagues used their testimony to laud his academic excellence in the hopes of convincing the judge to grant a lenient sentence.

Each of the professors stressed Lasaga’s potential to contribute to society through his pioneering research on global warming and hazardous waste disposal. Each also said Lasaga had a tendency to spread himself too thin with academic and social obligations.

“[He was] overcommitted,” said Hiroshi Ohmoto, a Pennsylvania State University geology professor who said he first met Lasaga while they were both students at Princeton University. “I don’t think he ever had time to look at all those pictures.”

Strollo said after the hearing that the testimony of Lasaga’s professorial colleagues was irrelevant.

“I have never heard comments so disconnected from reality,” he said, adding that Lasaga had remained self-absorbed and unconcerned with his victim’s welfare.

Strollo said Lasaga’s 11-page statement showed no remorse for his actions.

“He described himself as a superman, but he appears to be more like a villain,” Strollo said.

Evelyn Lasaga, the last to speak on her former husband’s behalf, focused on his success at keeping their family together, at least for a while, and said he was always trying to look on the bright side of life.

But she did say that Lasaga made egregious mistakes.

“He made some serious miscalculations,” she said, before turning quickly from his crimes to the topic of their failed marriage. “Above all, he didn’t pay attention to me.”

The one person who sat quietly throughout the entire ordeal was Lasaga himself. For the first time in his trek through the judicial system, Lasaga entered a courtroom clad not in his usual business suit but in a red baggy prison jumpsuit with chains around his ankles.

An incensed Polan said federal marshals misplaced Lasaga’s clothes and forgot to bring them to New Haven for sentencing.

“It was very inappropriate on the part of whoever was responsible,” Polan said.

Lasaga’s legal struggles may not be over. Polan has said she will appeal the 15-year federal sentence and seek a reduction of several years. And the young boy and his mother have filed a civil suit against Lasaga, the New Haven Board of Education, and Yale, seeking thousands of dollars in damages.