RIVERHEAD, N.Y. (CBSNewYork/AP) — A Long Island foster father who took in more than 100 troubled boys over 20 years is on trial on charges he sexually abused eight of the children.

In addition to the alleged abuse of the boys, prosecutors also say Cesar Gonzales-Mugaburu sexually abused a dog in front of a child.

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“The kids used to come by but they were never allowed to talk to anybody, probably because he didn’t want them to let the secret out,” neighbor Kathy Stein told CBS2’s Jennifer McLogan.

Opening arguments began Wednesday on Long Island. The trial could last a month or longer.

According to a grand jury report, Gonzales-Mugabaru fostered as many as 140 boys over two decades, despite having 18 separate open child abuse investigations.

Prosecutors say statute of limitation laws prevent them from bringing even more charges in the case.

Prosecutor Laurie Moroff called Gonzales-Mugaburu’s Suffolk County residence a “house of horrors,” where one of his eight victims was allegedly abused sexually for seven years.

“They lived in fear. They were afraid. They don’t function as you and I would function. They have low IQs and disabilities,” she said.

Moroff said Gonzales-Mugaburu would punch and threaten his victims is they did not listen to what he said.

“It was a horrific place to live,” Moroff said. “Eating on the floor, not allowed to do anything without asking for permission — including going to the bathroom,” Moroff said. 

The jury was told the Gonzales-Mugaburu was supposed to be the boys’ savior, but preyed upon them — treating his home like a candy store filled with boys, and more boys — isolating them and threatening them into submission.

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But defense attorney Donald Mates said the boys are all troubled and they are lying — some for financial gain, WCBS 880’s Sophia Hall reported.

“There’s a lawsuit going on, in federal district court, asking for money.” Mates said.

Gonzales-Mugaburu was given over $1.5 million in tax-free money for taking  in the foster children.

Before his arrest, Gonzales-Mugaburu was the subject of nine previous investigations involving alleged abuse dating back to 1998, according to a spokeswoman for Suffolk County.

Each of those inquiries led to a finding that the allegations weren’t credible, and none of them led to the removal of children from Gonzales-Mugaburu’s split-level ranch home in Ridge.

Gonzales-Mugaburu has pleaded not-guilty.

If convicted, Gonzales-Mugaburu could face up to life in prison.

The case against Gonzales-Mugaburu sparked an investigation into New York’s foster care system that found “abysmal” communication among the child welfare agencies involved in placing boys in the home.

The children will be called to testify.

The jury was also told the boys were forbidden to join after school clubs, play team sports, or have girlfriends.

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)