Thomas Datre Jr. pleaded guilty Wednesday to his role in a scheme to dump tons of contaminated material in Suffolk — an admission that spurred prosecutors in the six-week-old trial to drop all charges against his father.

Datre Jr. and his father, Thomas Datre Sr., had faced charges connected to the dumping of tens of thousands of tons of chunks of glass, concrete, cement and other contaminated fill at three sites in Islip Town and another in Deer Park.

Christopher Grabe, of Islandia Recycling, indicted with the Datres and three others in what Suffolk County District Attorney Thomas Spota had called a “greed-filled dumping scheme,” pleaded guilty to two felonies connected to the case as well as an unrelated felony criminal tax fraud charge.

Since the trial began in late February, Datre defense attorneys had sparred with prosecution witnesses, accused the pair’s rivals of cooking up a conspiracy to blame them for the dumping, and tried to discredit the testimony of consultants who collected soil samples at the sites.

Wednesday, a day after jurors were sent home because of what lawyers for both sides said was an effort by them and the judge to shorten the trial, Datre Jr.’s guilty plea ended it.

Datre Jr.’s attorney, Kevin Kearon of Garden City, pledged his client would follow through with a court order to help with cleanup efforts at the sites, even making use of his company’s machinery, operators and drivers.

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“He’s trying to demonstrate that his intentions were good at the beginning and they remain good now,” Kearon said outside court after the hearing. “We’re going to do everything humanly possible to assist in these efforts.”

Prosecutors had estimated their case, which began Feb. 23, would have lasted about three months. Defense lawyers for the Datres said if they presented a case, it could take another two months.

In front of state Supreme Court Justice Fernando Camacho in Central Islip on Wednesday, Datre Jr. pleaded guilty to four counts of endangering the public health, safety or the environment, a class E felony, in connection with dumping debris at the four sites.

Camacho told the Datres that because the son took full responsibility for committing the crimes, prosecutors would dismiss the charges against the father.

Andrew Campanelli, the defense attorney for Datre Sr., said his client “has maintained the position that he simply did not dump so much as a grain of sand anywhere, nor was he responsible for dumping anything anywhere.”

Campanelli also represents Daytree at Cortland Square Inc., whose owners are Datre Sr. and his wife, Clara Datre. Campanelli entered a guilty plea on behalf of the corporation to a charge of willful failure to pay prevailing wages. Camacho also deferred sentencing on that charge until restitution is paid to the workers, which was estimated to be from $80,000 to $90,000.

Datre Jr., his mother, Clara Datre, and his sister, Gia Gatien, had faced fraud charges stemming from the prevailing wage violations and theft from Islip Town. Because of the plea, the fraud charges against the three were dismissed.

Ronald Cianciulli and his company, Atlas Asphalt, along with former Islip Town Parks Commissioner Joseph J. Montuori Jr. and his former assistant, Brett A. Robinson — all named the indictment unsealed Dec. 8, 2014 — have open cases that are pending, a Suffolk district attorney spokesman said.

When he announced the indictments in 2014, Spota said they painted “a stark portrait of greed, abuse of power and corruption that resulted in an environmental catastrophe for the residents of the Town of Islip . . . for many years to come.”

Standing outside the courtroom nearly two years after his investigation began, Spota said Wednesday the dumping of contaminated materials is a statewide problem the Datre case brought to the forefront.

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“We have people who have admitted that indeed hazardous waste was dumped, which apparently was not their contention throughout, but they have admitted that now,” he said. “That’s what we’ve been saying all along. We were more concerned with the reckless conduct than any intentional conduct and I think that’s been established today.”

Guilty pleas by Datre Jr., the owner of 5 Brothers Farming Corp., and Grabe aren’t proof they knew the materials trucked from demolition and construction sites and dumped at the four locations contained hazardous substances, Camacho said. Their admissions did show that both men “were aware that there was a substantial possibility it was there” and they “disregarded” that risk, Camacho said in court.

The judge deferred sentences for Datre Jr. and Grabe with the understanding they will help with cleanup efforts at a 1-acre site on Sage Street in Central Islip, the wetlands in Deer Park, and Clemente Park.

If they comply, Datre Jr. could face between 1 to 3 years in prison and Grabe, six months behind bars with 5 years probation for the dumping charge, and another 6 months and 5 years probation for the tax charge related to the separate tax evasion case. Camacho also ordered Grabe to pay $57,244 in restitution on the tax charge.

Camacho called the deals “fair, reasonable and just,” and warned Datre Jr. and Grabe he intends to monitor their cleanup efforts closely and reserved the right to impose longer sentences if they fail to live up to the terms of the deal.

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“If you do positive things, constructive things to help remediate and repair some of the physical, emotional and psychological damage caused,” Camacho told them, “it could potentially be seen as mitigating circumstances.”