The young man sexually assaulted by former Saybrook College Master Antonio C. Lasaga testified briefly yesterday in the civil suit filed by his family against Lasaga and the New Haven Board of Education.

The man — identified in court as John Doe to protect his identity — spent less than five minutes on the stand in the third day of the trial. Jurors also watched portions of the pornographic video tapes Lasaga took of Doe during the time he was acting as the boy’s mentor.

Lasaga is currently in federal prison on a 15-year sentence for possession and receipt of child pornography, a sentence he is serving concurrently with a 20-year state sentence for the sexual assault. Lasaga defaulted on the civil suit, deciding not to defend himself, and jurors must only decide what damages he should pay the plaintiff.

Martin Echter, the attorney representing the Board of Education, is contesting the city’s culpability in the case. He has maintained that New Haven had no reason to suspect that Lasaga was assaulting Doe and that the mentoring program through which the boy met Lasaga was not affiliated with the city.

Doe was the last to testify Thursday, often giving one-word answers to the questions asked by his attorney, Frederick Trotta. Doe identified a photo Lasaga took of him and described what he wanted to do in the future, including his hope of becoming a state trooper.

The trial opened Thursday with Echter’s cross-examination of Lizzette Flores-Gregory, a worker with the Department of Children and Families. Flores-Gregory said her department never had any evidence suggesting Lasaga was molesting Doe, but she told a supervisor she thought Lasaga was “overinvested” in the boy.

“I had a bad feeling about this person,” Flores-Gregory said. “[But] we do things based on facts. We didn’t have any facts in this case.”

The jury also heard testimony from FBI Agent Lisa Tutty, the agent responsible for the 1998 search of the Saybrook master’s house that finally led to Lasaga’s arrest and conviction.

Tutty estimated that Lasaga had between 250,000 and 400,000 images of child pornography in the master’s house, including 76 images Lasaga took of Doe. Tutty said Lasaga willingly showed investigators the child pornography he had stored on his computer and on a number of disks, but did not reveal the existence of the videotapes of Doe, which agents found later.

Trotta then played segments of both videotapes to the jury and Judge Richard Arnold. Arnold said the first tape depicted Doe “posing in certain various stages of undress and revealing his buttocks and such to the camera.” Attorneys for the two sides agreed to stop both tapes after a few minutes, saying the content of the remainder of the videos was similar. Doe appears to be younger than 10 in the first video, Trotta said.

Tutty said the first video was taken in the Kline Geology Lab, where Lasaga worked, and the second was taken in the Saybrook master’s house.

The attorneys in the case said a city social worker, a teacher from the technical school he currently attends, and Doe’s mother are scheduled to testify tomorrow. Arnold said the suit could go to a jury as early as Tuesday.