Suffolk prosecutors charged a Sound Beach man Tuesday with vehicular manslaughter and driving while intoxicated, just as his trial on a lesser charge was about to begin.

The new charges against Christopher Campbell, 36, come almost two years after police say his box truck hit and killed Tracy Mangino, 40, as she walked on North Country Road near her Miller Place home. Campbell had been charged with leaving the scene of the October 2014 fatal crash and was preparing for trial when prosecutors got a new indictment with the increased charges.

If convicted, he now faces a maximum of 6 1⁄3 to 19 years in prison, instead of 2 1⁄3 to 7 years. His attorney, George Duncan of Central Islip, entered a not-guilty plea and later described the charges as a sign of “desperation” over a weak case by prosecutors.

Assistant District Attorney Maggie Bopp was reluctant to discuss the new charges both in court and afterward. During arraignments, prosecutors typically describe the basis of charges, but almost all of what Bopp said in court was in response to questions by state Supreme Court Justice Fernando Camacho.

He asked whether it was true that there was no scientific basis for the claim of intoxication — no breath test or blood test — and Bopp said that was the case. Camacho let Campbell remain free on $100,000 bail.

Later, she said that during trial preparation, witnesses described seeing Campbell intoxicated earlier that night. “It led to these charges,” she said.

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She declined to say anything about who the witnesses were, where they saw Campbell or how they determined he was too intoxicated to drive.

Duncan said the delay in bringing such charges and the reliance on nonexperts to determine intoxication were signs of a weak case. Even the original hit-and-run charge was unlikely to stick, Duncan said.

A video from a nearby home’s surveillance system captured the impact, he said.

“You can see her falling into the side of a two-ton box truck,” Duncan said, adding that the truck’s cab was past her when she fell. “The driver wouldn’t have seen, heard or felt the impact.”

Campbell didn’t become aware he may have been involved in Mangino’s death until he saw a news report describing the truck. He made no effort to hide his truck or to clean it — behavior typical of people involved in hit-and-run fatal crashes, Duncan said.

It’s a sign of weakness for prosecutors to now claim almost two years later that Campbell was intoxicated, Duncan said.

“I’ve never seen it done before,” Duncan said. “It indicates weakness in the overall case, and it’s a desperation move. It’s not a strong case.”

Regardless, Mangino’s family was thankful that police and prosecutors made the effort.

“They did a fantastic job,” said her father, Michael Mangino. “We’re very pleased.”

The victim’s daughter, Serena Mangino, 16, said she and her family were pleasantly surprised by the new charges.

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“We thought we were getting ready for trial,” she said. “We just want justice.”

She acknowledged they’ve waited a long time for justice, but said she hoped the wait would be worth it.

“They say good things come to those who wait,” she said.