Rabbi Yosef Kolko, 39, met the boy in 2007 at religious school-run summer camp in Lakewood where he was a counselor. The boy was 11 at the time, and authorities say abuse continued until early 2009.
Kolko has denied the charges, which include sexual assault and child endangerment.
The boy's former therapist testified Thursday that the boy told her in late 2008 he no longer needed help with his social skills because had had made a new friend, Rabbi Kolko.
"He's my best friend. He's the only one who understands me," Dr.Tsipora Koslowitz recounted the boy telling her.
Koslowitz said she told him that best friends were typically around the same age but he didn't understand.
At the end of a therapy session in February 2009, she said, the boy told her he had a secret. She said she had another patient coming in, so told him to tell her father. She said she thought it had something to do with bullying.
But that night, she said the boy's father called her to say it was about sexual abuse.
"He said it was Rabbi Kolko," she said.
The therapist did not report the allegation to authorities because for her, the allegation was only hearsay, she said.
Molestation, oral sex
The boy's father, also a rabbi, initially brought the allegation to a rabbinical court, or beit din. But unsatisfied with the way it was being handled, he took the case in mid-2009 to Ocean County prosecutors.
Prosecutors said the family was ostracized by the Orthodox Jewish community as a result. The family has since moved to Michigan.
A flier was circulated in Lakewood, a community with a large Orthodox Jewish community, saying the boy's father had made a mockery of the Torah and committed a "terrible deed" by taking the case to state prosecutors, the Asbury Park Press reported. The stance reflects beliefs among Orthodox Jews that conflict should be addressed within the community and the rabbinical court.
The boy took the witness stand Wednesday on the first day of the trial, testifying how he wanted to remain close to Kolko, even though his actions made him uncomfortable, because Kolko was his friend and he had no friends in school or camp.
The boy described a series of encounters with the rabbi, who would pick him up in his car, including molestation and oral sex and occurring in such locations as an empty classroom, a storage room, Kolko's car and the basement of a synagogue, the newspaper reported.
At one point, the boy testified, Kolko told him he was getting help and that if the boy talked to authorities it would ruin his career, the newspaper said.